media device collections are never organizable: remove a bunch of cruft

The only media device collection that was organizable was the UMS one
which was rewritten not to use media device collection (thanks, Bart!)
and is safe to assume that no new media device collections will be
organizable (in fact, the whole framework should be labelled
semi-deprecated)

Methods removed from MediaDeviceCollectionLocation we either made
unneeded or had the same implementations as superclass methods.

Copying/deleting tracks to/from iPod still works, BTW. :-)