fixing bug where deleted video files did not invalidate their cache.  Also stop auto-generating cache files by default, as it's very slow and videoscan is called as a function for update page loading.
Merge branch 'separate_sessions_cache' into videoscan_caching_bug

Conflicts:
	kalite/main/management/commands/videoscan.py
Merge remote-tracking branch 'upstream/develop' into videoscan_caching_bug
Merge remote-tracking branch 'origin/notify_user' into videoscan_caching_bug
duplicating change in another branch
fixing two caching bugs, based on deletion.  Adding test logic for setting up temporary cache and content_root, so test scripts of caching and video manipulation can occur without touching any existing cache items or videos.
set _web_cache on demand, to avoid errors when caching is disabled.
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into proper_browser_caching
added headers for doing proper etag and last-modified header checks
actually, that use of eTag was bogus.  Just depend on last-modified
fixed real problem--we simply should not allow browser-side caching.
removing conflicting Cache-Control settings.  DJANGO PLEASE ASSERT\! :(
Merge branch 'release-0.10' of https://github.com/learningequality/ka-lite into proper_browser_caching

Conflicts:
	kalite/main/tests/__init__.py
	kalite/securesync/api_views.py
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into proper_browser_caching

Conflicts:
	kalite/main/views.py
	kalite/securesync/api_views.py
addressing #484, fixing merge conflict issue
Completing tests, code review comments.

Conflicts:
	kalite/main/management/commands/videoscan.py
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into proper_browser_caching

Conflicts:
	kalite/main/tests/api_tests.py
	kalite/securesync/api_views.py
why is this so hard?  This time, an unwanted change seemingly out of nowhere.  we need the versioned serializers.
speechless.
removing print.  It's a bad morning.