WIP: Changing Student Anon ID Dump to return Course Specific IDs.

WIP: Going to verify tests pass, etc, but wanted to make sure this approach is sound before I burn too much time. 

@cpennington  Regarding our conversation this morning around the CSV action to pull anonymous user IDs, this PR would change the CSV to include the course-specific IDs. 

@Lyla-Fischer This change alters the contract of what is returned by this instructor dashboard action, is there any risk of impacting staff / instructors who may rely on the old Anonymous IDs? 

@wedaly