Added data migration for courses and announcements
Readded unique slugs
Added patch for slug field size migration. Added file headers for all migrations in the platform
Bugfix in activity creation handler for stats
Fixed data migration script for unique slugs.
Merge branch 'master' of git://github.com/OpenMOOC/moocng
Removed potential slug debug line
Fixed migration 14 for courses
Bugfix in mongo optmizations migrations
Command to fix bad ids in activities