This change adds a Django authentication backend which, when installed
will authenticate users based on their LTI identity rather than using
a username/password combination. The authentication method determines
first whether a user with the given username exists and, if so, whether
that user is associated with an LTI identity. It also verifies that
the LTI consumer and user ID passed to the LTI launch match those
stored in the LtiUser table. This will always be the case if the
authentication backend is reached through the LTI code, but it
provides an extra guarantee if the backend is called from elsewhere.

Improve structure cache metrics

Pass xblock parents

Improve the structure cache metrics with a course context, more standardized from_cache tag, and compression sizes

Fix XBlock inheritance ordering. XBlockMixin and derivatives should always come after XBlock and derivatives

User info cookie

Credit provider integration fixups

PHX-40 added the sorting of the most popular coupon codes used.

Remove restrictions on library creation in Studio (SOL-808)

Fixes DOC-1715, video doc is now in the correct RTD project

Gracefully handle credit provider keys with unicode type

MA-879 Fix bug in course_start_datetime_text

Release merge 06-24-2015

mattdrayer/SOL-449: Add flaky decorator to bok choy test

Moving xblock_user_state to edx-user-state-client, and add dependency to edx-platform

Update Bok Choy to run against optimized static files

Reverification flow asks for permission to use the webcam twice

TNL-2386

TNL-2465

Update URL when switching between Team tabs.

In-course Reverification checkpoint ask for the camera access twice on
Chrome.

ECOM-1739

Update credit eligibility

* Update credit eligibility when a user satisfies an eligibility requirement.
* Refactor set_credit_requirement_status arguments.
* Use django-simple-history to track requirement status changes.
* Refactor progress page by moving credit into a helper function and adding comments.

Move forgot_password_modal to login.html.

Delete LMS JS files that have no references to them.