player: allow loading of player with no video

We should have a way of loading just the player with no video. This can be loaded if the user then wants to upload a file to play with the player’s file input element.

This could be done by using the out parameter in the query only. If there is only one query parameter and it is 'x-motion-jpeg' (or other supported codecs in the future) then we just load the player since there is no more information to make a request to the data store.