secure-cookies: Allow to use secure HTTPS cookies (Django setting)

Cf https://docs.djangoproject.com/en/1.4/ref/settings/#std:setting-SESSION_COOKIE_SECURE
Update final text strings & readthedoc URL

TNL-401
Use ddt for shib tests
Remove test cleanups

Since `ddt` should make them unnecessary
Address PR review comments
Make student profile CSV download a background task, add cohort column
Merge pull request #5473 from edx/dan-f/background-student-profiles-add-cohort

Make student profile CSV download a background task, add cohort column
Merge pull request #5475 from edx/andya/cohort-doc-fixes

Update final text strings & readthedoc URL
Disable flaky JS FileUploader SystemFeedback and NotificationView tests
TNL-559
Convert acceptance to opaque keys
Fix course export/updates and upload CMS acceptance tests.
Fix cms hardcoded keys
Remove unneeded import
Teach mongo_connection to retry read operations in the face of AutoReconnect errors
Change email address detection in TinyMCE link plugin.
	- If link has a "@" and a ":", do not consider it an email address.
Add un-minified version of plugin.js file for link plugin.
Update build instructions to include media plugin.
Commit re-built minified JS.
Add all plugins to Jakefile.js in zip file.
Reason for this commit:
Split acceptance test was failing when TinyMCE detected a Split asset
key as an email address. Fix was to modify email address detection.
Fix hardcoded course urls
Fix error when doing non-ASCII forum search

Fixes TNL-160
Add cohort information to forum search events
Remove dead code
Add events for cohort modifications

This includes cohort creation/deletion and membership changes.