Updated the pagination tests to no longer use the toy course, but to instead explicitly upload the assets it needs.

 Added a new AssetsTestCase base class to own shared helper methods.

Fixing merge for sylvia's branch bld-615

Fixing merge for sylvia's branch bpd-615

Tests for behavior of export with & in HTML and XML-based components

Improvements to the i18n workflow tools.

Fix STUD-1129: handle out-of-range page numbers

Now any of the plurals being missing will count as an Empty translation,
and for looking at tags, the two English strings and all the translated
strings are mooshed together.

The tests in test_validate.py now examine the messages to see that they
have the right structure.  The English and the translation should have
the same tags, the translation can't be blank, and it can't have any
Astral plane characters.

Miscellaneous fixes to strings found during i18n work.

Assign valid content_type to static resource (import_static_content)

Add info about template for Checkbox problem type

Remove javascript_input and create_lti; add tools

Fix URI vendor module to be referenced via a relative URL.

Add more specific info about HTML+CSS+JS files, SOP

Django command to post submissions to ora

Don't catch all exceptions.

Modify server_track to handle being called without a request.

ORA-286

Add pagination to Studio's Files and Uploads page.

These changes are for STUD-813.

STUD-878

These changes implement STUD-813. The commit consists of the
following logical changes:
 - a REST API has been implemented for a course's assets
 - the page itself now fetches the assets client-side
 - the Backbone.Paginator library is used to support pagination
 - the AssetCollection has been refactored to extend
   Backbone.Paginator.requestPager so that it can be paged
 - an abstract PagingView class has been added to generalize
   the communication with a paging REST API
 - the AssetsView has been reimplemented to extend PagingView
 - two new child views have been added:
   - PagingHeader: the paging controls above the list of assets
   - PagingFooter: the paging controls below the assets

Add options to dump_course_structure to output inherited metadata.

LMS: Developer-centric Sass Area

Studio: Developer-centric Sass Area

* provides new .scss file for developers to add temporary/in-progress Sass for further refactor/polish
* cleans up note/import order in all application scss files