Fixed exception on the language page
Add cache debug panel

Updated django-debug-toolbar.  This requires a dev build command.

For some reason I couldn't use the provided cache panel, so I
implemented a custom one.

Put the debug toolbar at the top of the middleware.  This way it can
report on the code from other middleware classes.
Speed up cache fetches

Removed the code to get the language choices from cache.  The code is
dirt simple so it's probably faster to calculate that fetch from
cache.  I made it so it's still cached in local memory though.

Refactored CustomUser.get_languages to return language codes instead
of UserLanguage objects.  That's how we're using it anyways.  Also
make it use the new caching code so that it can be pulled in with
get_many()

Use video.get_workflow() to avoid fetching the workflow twice.

Updated amara-enterprise revision to pull in a fix there.
More cache fixes

Fix call to request.use_cached_user() it was happening in the wrong
view decorator.

Cache comments and invalidate the video cache when a comment is saved.

Don't cache the video page headers.  This breaks when the user
switches tabs.  Instead cache the video url and comment counts.

Use video cache when calculating languages for the upload subtitles
form

Removed the SaveUserIP and ResponseTime middleware.  I don't think we
use this data at all, it's potentially slow, and it's messing with the
caching code.

Bumping version to pull in a fix from amara-enterprise