Added tests for VideoLog and ExerciseLog saving, including 2 that fail.

Also, minor cleanup on imports on securesync tests. They still pass.
Added tests for creating/updating exercise logs via the API.

The updating test currently fails, due to a bug in the code to be fixed.
Added tests for video log saving, with wrapper for Client to do logins etc
Merge branch 'develop' of github.com:learningequality/ka-lite into fix_main_log_saving

Conflicts:
	kalite/main/tests/__init__.py
Fixes to address comments in pull request.
Merge pull request #342 from jamalex/fix_main_log_saving

Tests for the saving of video logs and exercise logs via the API or directly.
Awesome, woo woo! :)