Consistent configuration settings for MODULESTORE in both LMS and Studio.
Refactor get_parent_locations and users
STUD-1663

Conflicts:
	cms/djangoapps/contentstore/tests/test_contentstore.py
	cms/djangoapps/contentstore/tests/test_crud.py
	cms/djangoapps/contentstore/views/item.py
	cms/djangoapps/models/settings/course_details.py
	common/lib/xmodule/xmodule/modulestore/mongo/base.py
	common/lib/xmodule/xmodule/modulestore/mongo/draft.py
Enable Mixed Modulestore.

 #Fix test_sysadmin.py.