Add abuse flagging to discussion API

Flagging/unflagging is done by issuing a PATCH request on a thread or
comment endpoint with the "abuse_flagged" field set.

don't use hardcoded date in verification email test

Remove duplicate logged-in-cookie helper methods

Add followed thread retrieval to discussion API

There were two helper methods that set the marketing site
"logged in" cookie.  This commit deletes one of them
and ensures that all callers are using the other one.

pass debug option through to compile_sass

XCOM-416: Improved basket API's handling of embargo restrictions

This implements the "following" value for the "view" query parameter on
the thread list endpoint.

Update bok-choy version

Switch tabs to use ugettext_noop for titles.

adjust margin-bottom on courseware with license

Update the format of the credit provider timestamp.

Introduce caching of course metadata with app course_overviews

Fix JS tests that broke due to a conflict between merges

Correct logistration GET parameter preservation test case

Enforce MAX_COMMENT_DEPTH in discussion_api

Upgrade rednose to latest to fix bad output.

Use the number of seconds since the epoch (Jan 1 1970 UTC)
instead of an ISO-formatted datetime string.  This is easier
for credit providers to parse.

Reverification iOS support and refactor

Updates the XBlock utils requirement to the latest

Fixed two paly_video events emitted on video replay.

* Delete reverification templates
* Delete photocapture.js
* Delete unused "name change" end-points
* Rebuild the reverification views using Backbone sub-views
* Stop passing template names to the JavaScript code
* Avoid hard-coding the parent view ID in the webcam view (for getting the capture click sound URL)

Fix flaky test. SOL-975

This integrates the fixes from https://github.com/edx/xblock-utils/pull/20 and https://github.com/edx/xblock-utils/pull/21 - cf the PRs for the code review & +1s.

CC @smarnach @sarina

TNL-2166

Credit eligibility requirements display on student progress page