Improve Bulk Revert to properly handle all bundle-less entities

The current Bulk Revert functionality uses EntityFieldQuery to determine what data to remove. There's a problem in core (#1054168: EntityFieldQuery fails for entities that have no bundle) that means that any entity which does not have a bundle will return 0 results from the query. There is some hardcoding to make the functionality work with the User entity, but it needs to be generalized so it will work with other entities.