STUD-1404

This is the changes for STUD-1244, which introduces the ability for Studio to display
arbitrarily nested xblocks. In this change, a new container page is introduced which can
display nested xblocks. In particular, the xblock type of 'vertical' is special cased
to be shown inline as a collapsible section. The unit page is mostly unchanged, except
that container xblock's are shown as a link to their container page, rather than being
shown inline.

Add Studio client-side runtime notifications for saving/cancelling XBlock edits.

This requires fixing the javascript api implementation, and adding
an implementation of get_block to the ModuleSystem api.

However, the implementation is incomplete, due to mismatches between
the expectations of XModule and XBlock.

Also adds tests using the Acid block to make sure that the javascript
and python apis for children are working correctly.

This bug affected unpublishing content (and would trigger an error
message in studio). The fix was to uncouple the rendering of the studio_view
of an xblock with the student_view, so that content that wasn't in
draft mode already wouldn't be modified by early rendering of the
studio_view.

[STUD-1316]

This reverts commit b8da1c5b.

[LMS-1421][LMS-1517]

Make XBlock client-side runtimes proper classes, so that handlerUrl can
be defined in a per-runtime way, and we can have multiple runtimes on a
single page.

[LMS-1630][LMS-1421][LMS-1517]

STUD-1186

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

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

STUD-988

STUD-988

Add baseview(extended from backbone view), which can further extended by other views + Add fucntion to modify iframe and embed tags + add related tests
STUD-823

STUD-894

STUD-1040

Bug fix for dragging past last element in list.
STUD-879

STUD-945

STUD-844

STUD-946
STUD-947

STUD-850

STUD-293

STUD-848

Part of STUD-847.

html page and update access use 2 different urls
GET update can get an individual update
STUD-944

Part of STUD-847.