Fixed displaying video language codes.

This changes things so we correctly display codes not in the 'unisubs'
mapping (codes not normally given as choices for the user).
Don't do indexing inside the move_videos view

Using the video_changed_tasks task moves the work to the worker
process which is much nicer.
Bunch of documentation fixes
Logout users to the home page (#1838)
Merge pull request #1850 from pculture/video-language-code-display

Fixed displaying video language codes.
Bumping versions
Merge pull request #1847 from pculture/gh-1837

Don't do indexing inside the move_videos view