Fixed minor bug with bus polling...

On my Fedora 19 resintall (don't ask), I have gstreamer 1.0.10 by default, and
a poll with Gst.MessageType.Any results in

ValueError: 0 not in range 0 to 18446744073709551615

So, I just poll for specific messages for now.
Re-wrote the controller code to work with gstreamer 1.0...

but, sadly, we still seem to have the lurking volume discontinuity :-(