remove unnecessary code, and clarify what it's doing.

wiki middleware fix (LMS-2461)

CourseRole names have a new format (type_org.number.run). Previously
when checking if a user was staff for a course wiki type_org/number/run
and type_number format role names were checked by parsing user group names.

This logic has been refactored to first fetch all courses which use the
particular wiki_slug and then use courseware.access.has_access to check if the
user has staff permissions on any of the courses.

LMS-2136

STUD-1006

All the dialogs in the wiki are now accessible to screen readers.

Also, the "Switch to selected version" button did the odd thing of
reloading the page with the new version selected, but inside a dialog.
That is now fixed.

The merge dialog has a warning that looks kind of funky still, but you
can read it, unlike the previous code.

LMS-1337

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.

LMS-1355

LMS-1307

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

add fixes for 500 bugs (lighthouse 287 and 293) by requiring login for accessing licenses and inline discussions.  Add unit tests for licenses, and rearrange tests based off of (the former) PageLoad.  Also cleanups for pylint and pep8.

append some character, in this case a '_', if the course number is really a full-on number. The Wiki library interprets this incorrectly - to date we've always used non-numerical values.