Story #4: Coaches sees grades.

Story #9: Coach downloads grades.

Implelement test coverage for utility code supporting enrollments in CCXs

bugfix: prevent UnboundNameError if user does not exist in database.

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.

Make e-mail activation optional

Fix i18n breaking in some js and underscore files

Add i18n_fastgenerate

use different queue for smaller emails (TNL-1591)

Redirect Enrollment API to Platform API doc

Update translations (autogenerated message)

Add mentoring v2 and its bump dependency xblock-utils for Harvard

1. Spliting strings inside the call to `gettext()` in javascript breaks the string extraction process, so the string should kept in one line.
2. Using escape string inside a string in `gettext()` may cause the extractor to misunderstand the escape string, so that it will escape this escape string.

So the time-consuming i18n_extract step can be skipped for situations that only the translated strings are modified while the source strings are still the same.

Merge release back into master (hotfix-2015-04-03)

Hotfix: Add proxy to allow IE9 to make xdomain requests

Move debug toolbar to end of devstack middleware

Update SKU field help text and verbose name

The django debug toolbar circumvents other middleware with process_view
functions, so it needs to go at the end of our MIDDLEWARE_CLASSES
setting.

https://django-debug-toolbar.readthedocs.org/en/1.3/tips.html#middleware-isn-t-working-correctly

Fix duplication of Randomized Content Blocks

Update XBlock Hash

PLAT-520 Fix Asset store import of null values.

Adds an /xdomain_proxy.html endpoint that serves
the proxy file from the xdomain library.  This
allows IE9 users to iframe in the proxy page
to simulate a cross-domain request with cookies.

Reverts removed styling rule which broke certificate status message on the course dashboard

Add social sharing feature (Twitter, Facebook) to student dashboard

Ignore pylint error 7610 (translation-of-non-string) on where it is intended

Fixed invalid `usage key` errors which previously throw 500.

As some i18n features need ```ugettext``` or its shorcut ```_``` to be called on a non-string-literal, so the pylint check of ```translation-of-non-string``` should be explicitly disabled in such situations.