Added a bunch of tests for translation tasks.

Made tests use the test_factories module to create objects instead of
teamstestsutils.  Made default password "password" for users in
test_factories.

Fixed return value for Task._complete_subtitles().
Refactored code to simulate the editor widget for tests

Moved it into the tests module and tried to generalize it a bit.
Seems like other test code could definitely make use of this.
Made tests for translations.