Worker for deleting images

[gmanley]

After I move over to using foreign keys images will be dependent: nullify on the foreign key level. The idea is to create a worker that is set to run on a schedule that finds images with no album_id and delete them. This includes making the call that removes them from the file store. This is a better way to do it as deleting of images is super slow as it blocks on the network call to remove them from a remote store.