Enable tests modules to auto-import all test files in their directories.
wrap all API calls with error catching, so all API return Json-based errors
update video_download
raise Http404, not return
Merge branch 'develop' of github.com:learningequality/ka-lite into safe_api_errors

Conflicts:
	kalite/securesync/api_views.py
updating formatting on video_download
apply 'moviecounts' changes to the homepage.
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into testing_testing

Conflicts:
	kalite/central/tests/__init__.py
	kalite/main/tests/__init__.py
	kalite/securesync/tests/__init__.py
Added a helper function for importing * from all modules in a directory.
Tweaks to auto-import function.
Tweak to docstring for import_all_from function.
Removed "exclude_special_modules" param from "import_all_from".
Merge branch 'testing_testing' into release-0.10
Merge branch 'release-0.10' of github.com:learningequality/ka-lite into release-0.10

Conflicts:
	kalite/main/tests/__init__.py
Added basic Google Analytics tracking to the update page.
essentially re-applying commit dc1c4a01d020a822affe21aec77a4faa2335c4c7, to set id=slug
updating topic data to fix regression bug.
Redid update page Google Analytics to set variables via template tags.
Merge pull request #455 from bcipolli/id_vs_slug_regression

Id vs slug regression
making strings more i18n-friendly, being careful to only display a single error of a single type.