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.

Adds configurable middleware in common/djangoapps/embargo that
allows specific courses to comply with US Export regulations by
embargoing students from specific countries, whilst simultaneously
allowing other courses to be freely open to all.

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]

styling for recursive xblock rendering structure to be used in the container page, pulling from general xblock styles in a separate file.

All forward facing wording changed to Export to Git
Export to git functions removed from management command and put in common file
Additional error checking and documentation improvements
Nitpicks and other minor fixes

Added tests
Converted scripts to django commands
Removed advanced module requirement
Generalized to platform
Switched to subprocess for shell commands
Beefed up resiliency and error checking.
Refactored since #1910 removed get_location_and_verify_access
Added settings to aws for export directory and reworked test setup and teardown
Several review based fixes
Added line to Changelog
Changed URL handler to be accepting and moved git bare repo inside of test_root/data
Added exception logging to help trace issues
Added output in exception logging
Made the branch to commit to explicit instead of implicit
Skipping git identity test on condition of global configuration set

[LMS-1614]

STUD-945

STUD-948

STUD-844

STUD-946
STUD-947

STUD-850

STUD-849

STUD-848

Part of STUD-847.

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

Adds xblock handler_url support to the LMS, and makes handle_ajax use
that code.

[LMS-230] [LMS-229]

Part of STUD-847.

STUD-846

Move index access into the url
Move course creation into the url
Add helper methods for testing to serialize json data and set accept header.

Move RESTful URLs into our "done" section.

To help fix recent bugs re orphaned discussions and
to prototype a more restful json oriented api.