Implementation of Video Queue (show queue, add and remove entries)

I chose to create a resource under user to allow access to queues using routes that include the user ID.  But I also kept the my_queue route at root which is sent to the same controller.  The controller is tolerant of an omitted user_id and assumes it to mean the current logged in user.  Note that this complicated my test writing so I had to write extra tests for various cases of user_id supplied and omitted.

It may be provided in the POST.  Currently, in the UI this may be omitted, but via non-browser HTTP requests in the future I'd wanted to still support possibility that position is explicitly supplied.