Changing Student Anon ID Dump to return Course Specific IDs.

Tests verified, manually tested.

@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