STUD-714

[LMS-226]
[LMS-2013]

Added sorting to the new pagination logic for STUD-995.

STUD-1072

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.

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

Part of STUD-91

on new Locators to make it clear that they have a different syntax
than Location.course_id altho they represent the same info.

[LMS-1614]

and fix found errors.

STUD-1063

Refactored stub services for style and DRY

Added unit tests for stub implementations

Updated acceptance tests that depend on stubs.

Updated Studio acceptance tests to use YouTube stub server; fixed failing tests in devstack.

usage_id implies self-sufficiency. The block_id is relative to its structure.

STUD-1048

For seeing overview of system status, for deleting and loading
courses, for seeing log of git imports of courseware.  Includes command
for importing course XML from git repositories.

Added a lot of tests for additional coverage with some minor fixes
those tests discovered

STUD-1039

Conflicts:
	cms/djangoapps/auth/authz.py

STUD-1039

STUD-1030

Conflicts:
	cms/djangoapps/auth/authz.py

STUD-1013

LMS-1551