Remove the use of celery.group from bulk email subtasks.

Improve forums performance

Avoid recomputing course module information for every thread, which
should dramatically improve the performance of high-percentile latency
queries.

JIRA: FOR-250

The _DISCUSSIONINFO global was originally used as a cache, but has since
lost that capability and is therefore just harmful. This is a precursor
to more refactoring that will improve the performance of the forums and
may itself provide some performance improvement because it separates the
computation done by two functions that each previously computed the
entirety of _DISCUSSIONINFO.

Improved release script

Allow the export_course command to dump results to stdout

This is in preparation for significant refactoring of the code in
question.

Improve forum error handling

Add explicit wait to JS transcript tests

CommentClientError now has sane subclasses that are meaningfully
distinct, and each subclass is handled appropriately. Errors raised by
the requests library are no longer handled by turning them into
CommentClientErrors, since there is no meaningful handling we can do,
and this way we will get more visibility into why errors are occurring.
Also, HTTP status codes from the comments service indicating client
error are correctly passed through to the client.

Cheatsheet modal is accessible. LMS-1303

Add css mode to the compressed file.

Commit/rollback transaction after rendering response to prevent TransactionManagementErrors due to db access in templates.

Fix for static path parsing

Use the leanModal stuff to show the cheatsheet dialog in the wiki.

LMS-1303

When a url contains a query parameter it gets incorrectly parsed
when replacing the /static portion.

This fix handles urls with query parameters.

STUD-833

test bucket existence before creation

Prevent unbounded nesting of lms field_datas

Previously, whenever a XModule was created from a XDescriptor, we
created another level of nesting of FieldData objects. This change
prevents that nesting.

[TKTS-393]

Also let xml import work on modulestores that don't use write signaling

student.views.confirm_email_change: commit/rollback transaction after rendering response instead of before

student.tests: Added db access in mock_render_to_response() to test any issues with @transaction.commit_manually

Add masked input back into RequireJS

Add skip links to both CMS and LMS

Bug: LMS-1311

LMS-1311