Mark MediaObject, MasterFile, Derivative, and Admin::Collection as migratable
First stab at R1=>R2 MediaObject, MasterFile, and Derivative migrations
Remove collections from descMetadata after assigning Collection objects
Smarter, just-in-time collection creation
First cut at a migration of the system groups
Add 'ActiveRecord' migrations for avalon.yml and MediaObjects.
Don't change discover/read rights if the object already has explicit ones defined
Replace the 'collection_manager' group with 'manager' in object rights
Create an administrator group if it does not already exist and use the first person in group_manager as the default value