Next gen modulestore

Will/fix acceptance tests

Renzo/in context progress

Fix/foldit leaderboard

set django-wiki to its most recent version

Simple port of Class2Go's chat feature

A new modulestore backed by mongo that changes the data format to
facilitate easy versioning, sharing content between courses, and fast
lookup of course structure and Scope.settings data.

Conflicts:
	cms/djangoapps/contentstore/tests/test_contentstore.py

POST requests were claiming request.method == 'PUT'

Fix/vik/studio oe

Ned/studentmodulehistory cleaner command

So, changed handlers to look for either value.

Bug report: remove <?xml version..> tag

Fixes code_jail imports and draganddrop yaml

I18N work seems to have lost a very prominent space in the landing page

add a new django-admin command to dump out a course structure document. ...

https://edx-wiki.atlassian.net/browse/STUD-428

Rebase on today's master and update to unit test to include settings
where needed.

Only render the chat widget if both the site has enabled it in the
`MITX_FEATURES` and if the course has enabled it. In addition, fail
gracefully with a log warning if the `JABBER_DOMAIN` is not set, and
do not try to render the widget. However, do go ahead and render the
rest of the courseware.

To protect against chat blowing things up, we include a way to
enable and disable it on an entire site-wide basis.

Ensure that the chat connection settings are generated properly for
the template context.