The identity element should be handled by the GstBin's cleanup,
removing it on the remove_elements function might remove it
too soon, as this function can be called directly from playsink
The playsink was nastily poking a boolean in the structure.
Make those booleans properties, so we are told when they change,
and rebuild the conversion bin when they do.
Some cleanup to go with it too.
https://bugzilla.gnome.org/show_bug.cgi?id=661262
ie, audio/x-raw- for audio, video/x-raw- for video.
Add a trailing - to be more specific. I doubt there's anything
like audio/x-rawhide or something, but you never know.
https://bugzilla.gnome.org/show_bug.cgi?id=661262
