STUD-1006

Also cleans up test_view_authentication to use user factories for
various user classes

This centralizes the logic for group membership, and means that we
don't need to make queries to find out whether the legacy groups names exist.

Modified navigation tests to use MixedModulestore
Updated factories to find editable modulestore

Updated test_submitting_problems

Updated test_tabs.py

Updated test_view_authentication

Updated test_views

Updated courseware/tests/tests.py

Updated test_masquerade

Updated test_module_render

Pylint fixes

Updated video and word cloud tests

Updated course wiki tests

Updated license and open_ended tests.
One open_ended test still failing due to Mako initialization issues

Updated staticbook

Updated django_comment_client tests

Updated instructor tests

Updated instructor task tests

Updated external_auth tests

Updated course_groups

In the middle of addressing pull request comments. This is a safety commit in case I have to revert some changes I'm about to make.

Conflicts:
	lms/djangoapps/courseware/tests/test_navigation.py
	lms/djangoapps/courseware/tests/test_view_authentication.py
	lms/djangoapps/courseware/tests/tests.py