Merge hotfix-2016-06-10 release into master

AC-414 adding headings as first child to sections

Hotfix for GET to POST

Repair platform API documentation build

Ensure split-test group zero content is protected

Mocked some Python modules when running a Sphinx documentation publishing build. Updated an autoclass class name that changed."

New XBlock Configuration Models

TNL-4771

TNL-4666

Enable concurrency (but not randomization) in LMS unit tests

AC-473 fixing width of closed captions in fullscreen

Clean up the help tab Sass included on Pattern Library pages

* Initial lms changes for Sailthru

* Fix identified code quality issues

* Fix migration failure

* Fix code quality identified issue

Rename i18n.tests to i18n_tests, so that the i18n.tests package can be a package without squashing the python i18n package namespace

Fix 500 error when searching for a user without catalogs.

Update translations (autogenerated message)

Use cached data to find completed programs on LMS

ECOM-4653

Enable randomization (but not concurrency) in LMS unit tests

Dont leak current requests in tests

Update translations (autogenerated message)

Use v0.3.2 of i18n_tools

Use a contextmanager to cleanup after manipulating the current request in create_account tests for external auth

Use a contextmanager to cleanup after manipulating the current request in password_policy tests for external auth

These changes improve the performance of the LMS' program certification task. They also reduce strain on the programs service, especially when attempting to award program certificates to large numbers of students. ECOM-4490.

Correct destination of management command args.

enforce display name in CAPA problems