Also contains:

* mattdrayer/rebase-20140722b: cherry-pick 0325694
* mattdrayer/rebase-20140722: cherry-pick e8b1217
* Sessions API Documentation
* mattdrayer/rebase-20140722: cherry-pick ofao48d
* mattdrayer/rebase-20140722: cherry-pick b0c343c
* mattdrayer/rebase-20140722: cherry-pick d56e973
* mattdrayer/status-500-fix: Small API bug
* added content_id to workgroup review submissions
* mattdrayer/api-user-preferences-delete: Added new Detail view, GET/DELETE operations
* mattdrayer/rebase-20140722: cherry-pick 0624385
* handle exception if user never accessed any course module
* mattdrayer/rebase-20140722: cherry-pick caada51
* cdodge/add-progress-publish-api-endpoint: expose a new xblock runtime publish special cased event type 'progress' which adds an entry into the CourseCompletions table
* add default setting for feature flag in common.py
* mattdrayer/rebase-20140722: cherry-pick 7a1e12c
* mattdrayer/rebase-20140722: Functional stabilization

cdodge/fire-progress-on-html-module-render: modify the xmodule HTML to fire a progress event to record the fact that the user visited that content

Included commits:
* xblock-external-ui: Include CSRF token in the API answer
* xblock-external-ui: Adds support for CORS headers (cross-domain request)
* xblock-external-ui: Include full path when building local_url
* xblock-external-ui: Fix TestHandleXBlockCallback & bok_choy, add tests
* xblock-external-ui: Only return `instance` in `_invoke_xblock_handler()`
* xblock-external-ui: Group resources by hash tag to avoid duplicate loads
* xblock-external-ui: Alternate referer check for CORS requests
* session-cookie-httponly: Allow to disable httponly on session cookies
* remove errant log message
* xblock-no-anonymous: Fail early if the XBlock view is called anonymously

The only consumer of that functionality (the XQueue callback) already
does retries, so newly introduce integrity errors (due to multiple
commiters trying to update a StudentModule) won't break the XQueue
processing pipeline.

Currently, all XBlock/XModule handlers are lumped together in the
same transaction (courseware.module_render:handle_xblock_callback).
This makes it difficult to pinpoint problems with specific handlers.
With this change, the transaction name will now look like:

  OpenAssessmentBlockWithMixins.save_submission
  CapaDescriptorWithMixins.xmodule_handler/problem_show

fix for making sure all descriptor fields are always available for course descriptors despite module_class tricks

add required fields to cache data for tests

use a different strategy to mock up the get_children method

Switch to font awesome icons, to fix issue with toggling collapsible sections of the schedule in ccx coach dashboard

Ensure access check takes place after descriptor is bound to the user, or field override checks will never happen

This feature provides the ability to designate a "coach" who can create customized runs of an existing course, invite students to participate, and manage students through the run of the course.

In this squashed commit we implement the initial scifi, add the 'POC Coach' course role, refine the scifi, add migrations for models, create POCs, enforce POC Coach role, provide panels for Coach Dashboard, set up rudimentary display of course outline, add and remove units, show/hide all units, and save schedule changes, set dates when adding units, edit dates on units already added and provide some tests.

We also provide mechanisms for invitation and enrollment in a POC (to become CCX) and control the display of blocks to students in a POC.

individual students, and a reimplementation of the individual due date
feature.

This work introduces an architecture, used with the 'authored_data'
portion of LmsFieldData, which allows arbitrary field overrides to be
made for fields that are part of the course content or settings (Mongo
data).  The basic architecture is extensible by means of writing and
configuring arbitrary field override providers.

One concrete implementation of a field override provider is provided
which allows for overrides to be for individual students.  This provider
is then used as a basis for reimplementing the individual due date
extensions feature as a proof of concept for the design.

One can imagine writing override providers that provide overrides based
on a student's membership in a cohort or other similar idea.  This work
is being done, in fact, to pave the way for the Personal Online Courses
feature being developed by MIT, which will use an override provider very
much long those lines.

TNL-1736

- added entrance exam check on course info
- staff can by pass gating and added tests
- refined gating logic
- changes after rebasing with Asad's branch
- check ENTRANCE_EXAMS feature is enabled
- updated test to reflect new logic
- catering anonymous user in entrance exam permission
- fixed broken tests
- change after feedback on 16/3
- fix for a broken test
- created new entrance_exams module
- fixed quality error and improved test coverage
- put get_required_content back in milestones helper
- Refactored entrance exams logic
- Refactored tabs logic
- Fixed broken unit test
- changes after feedback from dan-f on 3/27
- removed unnecessary user.is_anonymous check
- Addressed PR feedback
- Addressed commit-specific feedback
- Rework guard clauses
- Add coverage for course info case

Multi-commit history:
- hide drag functionality for entrance exam section.
- hide entrance exam subsection elements e.g. delete, drag, name etc.
- show unit/verticals expanded in case of entrance exam
- modify code in order to allow user to update entrance exam score from UI.
- write down unit tests.
- write down Jasmine tests.
- add bok-choy test
- updated bok-choy test
- internationalize string
- repositioned sequential block creatori
- SOL-221 (entrance exam message)
- SOL-199 LMS Part (show entrance exam content) and hide the course navigation bar.
- redirect the view in case of entrance exam.
- update code structure as per suggestions
- write down unit tests
- fix pep8
- instead of hiding the exam requirement message, now also showing the exam the completion message (success state).
- write down unit test to show exam completion message.
- Update code as per review suggestions
- update doc string
- addressed review suggestions
- change sequential message text
- css adjustments
- added new css class for entrance exam score in studio
- added Jasmine test for remaning coverage
- sequential message should appear under the context of entrance exam subsection.
- updated text in CMS and LMS as per suggestions.
- added unit text to insure sequential message should not be present in other chapters rather then entrance exam.
- skip setter if empty prerequisite course list
- exclude logic from xblock_info.js that is specifically related to entrance exam.
- added js tests and updated code as per suggestions
- added tests
- addressed several PR issues
- Several small fixes (style, refactoring)
- Fixed score update issue
- added some more unit tests.
- code suggested changes.
- addressed PR feedback

Conflicts:
	lms/djangoapps/courseware/courses.py
	lms/djangoapps/instructor_task/api.py

refined entrance exam student attempts reset

Quality improvements 1/16

added rescore, delete state and task history functionality

added unit tests for entrance exam reset attempts

added unit tests for re scoring of entrance exam and task history

improved test coverage

Got rid of pep violation

feedback changes and added jasmine test

added more jasmine tests for Javascript changes

added bok-choy tests for UI changes

replaced input containing <p> tags with <label>

Removed ee element assertions to avoid js error

Added call to super.setUp()

changes based on feedback on 2/18

Writing tests in JS instead of coffee script

commit related to skip entrance exam 2/13

fixed bad-continuation quality error

fixed broken bok-choy test

changes based on feedback on 2/18

added js tests and removed coffee script tests

fixed broken bok-choy and unit tests

changes left while rebasing

rephrase test titles

do not need these libs

changes based on feedback on 2/24

changes text which was left

Changes based on feedback on 3/3

xblock-external-ui: Alternate referer check for CORS requests
xblock-external-ui: Allow to disable httponly on session cookies
xblock-external-ui: Add a unit test for CorsCSRFMiddleware

xblock-external-ui: Include CSRF token in the API answer
xblock-external-ui: Include full path when building local_url
xblock-external-ui: Fix TestHandleXBlockCallback & bok_choy, add tests
xblock-external-ui: Only return `instance` in `_invoke_xblock_handler()`
xblock-external-ui: Group resources by hash tag to avoid duplicate loads
xblock-external-ui: PEP8
xblock-external-ui: Fail early if the XBlock view is called anonymously

    We used to serve anonymous requests, but most XBlocks assume that the
    user is logged in, which can generate a lot of errors when the user is
    accessed or when an XBlock ajax callback is queried. Fail early to only
    get one error per page load, and prevent displaying the XBlock
    altogether when the LMS doesn't find an active user session.

xblock-external-ui: Add request params in view render context
xblock-external-ui: HTTP error status when file is too large for handler
xblock-external-ui: Fix unicode encodings in XBlock rendering
xblock-external-ui: Feature flag for API call ENABLE_XBLOCK_VIEW_ENDPOINT

get the raw DescriptorSystem, not the CombinedSystem when instantiating xmodules (TNL-1226)

quality fixes

remove trailing comma

TNL-836

returns XBlockuser with 2 data layers

TNL-651