AFT WORKS!
For parts of it at least.
Move your files around and watch as the playlist automagically keeps working :-)

Next up is getting lyrics and statistics back up, although that should be relatively trivial.

One issue currently: the behavior for the OSD when notifyObservers is called is to pop up.

This should probably be changed, as it's probably not what we actually want - if the currently playing track is the one that was changed, only in that case should it pop up.