resolve conflict on rebase
some cleanup
STUD-1133
added test for course listing
STUD-1133
pylint fixes
STUD-1133
update course_listing function and tests
STUD-1133
add mangement commad to update entries in loc_mapper with 'lower_id' and 'lower_course_id' + update _accessible_courses_list_from_groups to get courses with lowercase ids
STUD-1133
replace 'get_items' with 'get_courses' +  update "loc_mapper" for all user courses
STUD-1133
add lower course_id as key in loc_mapper cache to get courses with lower id
STUD-1133
add performance test for course listing
STUD-1133
some cleanup
STUD-1133
code update/cleanup
STUD-1133
pep8 fix
STUD-1133
import UserFactory from student module
STUD-1133