Fix bug with loaded response on file tracks.

In addition, the type is now provided as :type, not :track.
Remove duplicate controller callbacks.

Also added a debugging callback for loaded.  This will disappear soon.
Fix accidental use of in?.
Separate and merge request/response codes.

Codes are now in a separate file, baps_codes.

In addition, the response parser has been separated from the
response structures and ResponseType has been removed.

Changes elsewhere have been made to accommodate this.