Arvados

manifest_locator() shows the uuid of the collection, but may not be obvious to all users. Consider adding the method uuid() because we have we talk in uuids and portable_data_hashes, and there's already a method called portable_data_hash().

Also consider content_address() with an output that's the same as portable_data_hash() because in workbench we call the portable_data_hash a content_address.