|Component:||Entity CRUD controller|
Currently the provided CRUD controller does not yet support revisions.
* Add another controller class inheriting from the EntityAPIController, so we don't need to bother changing stable code.
* Provide a set of useful API functions, entity_delete_revision(), ..?
* Implement tests.
* Should the entity type specify which properties are revisioned? Should it have to create the table, or should we auto-create it with the same properties as the main one?