Merge pull request #2163 from jomel150/playlists

Backbonify PlaylistsTableView in homepage
Some unit tests for exam page redirect of students if teacher enables exam mode.
fix the start of downloading of language packs
Merge branch 'nalanda-rct2' into feature/2122-Exam-list-page
Refactor and add more unit tests for exam page feature.
Merge pull request #2166 from aronasorman/2158

Disable some deletion features for teachers
Skeleton for exam coach report
Refactor exam unit tests and initial attempt to make some codes reusable.
Rendering table correctly.
Inheriting navigation between facilities and groups correctly
Table rendering complete with summary stats (max, min, etc)
Fixed the modifymodel management command to actually modify model.
Reduce noise in test output.
Test detail page is functional
A tiny refactor and style tweaks.
'Overall' stat working
Cleaning and refactoring ecosystem tests, and beginnings of new test.
Fix problem which raises exception when `python manage.py kaserve` is ran.
Refactor exam page tests to get the initial browser test working.
More browser tests for exam mode feature.