Removed unnecessary settings wrangling from ModuleStoreTestCase.

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
Merge branch 'master' into will/use-mixed-modulestore-in-tests

Conflicts:
	common/lib/xmodule/xmodule/modulestore/django.py
	lms/djangoapps/courseware/tests/test_views.py
	lms/djangoapps/courseware/tests/tests.py