TNL-1459

Add ENABLE_DISCUSSION_EMAIL_DIGEST feature, to enable discussion emails digest by default for all users

Handle the case in which a student reverifies after the verification
deadline has passed.  This will display the user's status as "verified"
on the dashboard even if they technically missed the deadline.

TNL-1419

TNL-1202

TNL-1451

xblock-external-ui: Alternate referer check for CORS requests
xblock-external-ui: Allow to disable httponly on session cookies
xblock-external-ui: Add a unit test for CorsCSRFMiddleware

It looks like one version of the class was first added [1] and then a
few days later, another was written [2]. The newer declaration appeared
lower in the file, allowing it to hide the other.

This removes the first, hidden declaration.

[1] commit 7aa493ec
    Date:   Fri Mar 1 10:36:20 2013 -0500
[2] commit f62dad2f
    Date:   Tue Mar 5 16:31:02 2013 -0500

When the list is empty in discussion blackout
on studio side it causes the exception on lms
side when we try to access the discussion. We
were expecting the values and try to parse it
in two values start and end date whereas parsing
empty values to two values causing the exception.
Now values will be parse when value exists. Empty
value will be ignored.

TNL-1390

Add "source" parameter to LinkedIn add-to-profile URL.

Add platform name to certification name.

Style changes for linked in sharing on dashboard

- Added tests
- Updated model field specification
- Fixed issue of multiple event emission
- Updated admin page
- Added management command to manually generate course structures

contextmananger. Add ddt to mongo call count testing.

JIRA: MA-286

3 line patch, together with a world of pain due to buggy code, broken abstractions in tests, etc.

Users who are blocked from enrolling in a course
due to an embargo are redirected to the blocked
message page after authentication completes.