Allowing file based submissions for ORA2

Allows upload via fileupload service, implemented to use s3
UI is pretty basic for now. Allows upload, viewing images from the same service.
@wedaly 

If we're able to pass this in explicitly, it's probably worth making this a separate setting specific to the file upload service.  (The reason we can't do that elsewhere is that we're using Django storages, which assumes there's only one bucket available.)