Merge pull request #2292 from learningequality/nalanda-rct2

Nalanda rct2 to central-master
Merge pull request #2301 from learningequality/nalanda-rct2

Nalanda rct2 into nalanda-prerelease
Merge pull request #2302 from learningequality/nalanda-rct2

bring back the old seeds for the baseline exams, as some teachers have a...
Merge pull request #2306 from learningequality/nalanda-rct2

Nalanda rct2 into central-master
Merge branch 'nalanda-rct2' into central-master
Merge branch 'nalanda-rct2' of github.com:learningequality/ka-lite into central-master
Update management command to validate nalanda playlist data
Merge remote-tracking branch 'upstream/nalanda-rct3' into quiz-in-student-report
In progress: migrating student reports from topic tree to playlists
A bit of styling progress.
Allow teachers to perform a forced sync via web interface button.
Make AttemptLog.context_type optional to avoid sync errors on old data.
Merge branch 'nalanda-rct2' of github.com:learningequality/ka-lite into nalanda-rct2
Merge branch 'nalanda-rct2' into nalanda-prerelease
Merge pull request #2318 from learningequality/nalanda-prerelease

Nalanda prerelease to central-master
Class for aggregating user playlist progress for API results
Ahaha. If it's not broken, fix it. If it is, fix it too.
Merge branch 'release-0.12.0' of github.com:learningequality/ka-lite into central-master
Moves basepoint modifying code into api_views.
Modifies points based on currently set unit.
Exposes playlist unit property.