Add Draft module store that is used whenever any item is update in the CAS (but not during import, and not for templates)

respond to Cale pull request comments. Update access.py (LMS) to use the same 'check for legacy group name first' logic. Add SECRET_KEY setting to the CAS project so that auth tokens from CAS are accepted in the LMS

adhere to the naming conventions of user groups (instructor_* and staff_* of the LMS AuthZ implementation). While we're keeping our authz.py implementation - which is duplicative of LMS's access.py - in order to minimize code churn/risk-of-regression, there is data compatibility so the two systems will interpret the data the same way

Make imports into the CMS ignore broken modules, while still loading bad xml as error modules in the LMS

Sketchy adding of test dbs to the cms test.py config file -- these are required for the Student (shared django app) tests to run