refactoring EngineController to depend directly on Phonon

[Ian Monroe]

What do people think about not using plugins at all for our audio
backend? I was actually arguing against this idea with Max K just a
couple of days ago. But then I looked at trying to fix some of the
issues with the phonon backend and noticed what a mess
EngineController is. I also noticed that not much calls
EngineController really (just its currentTrack method), so I don't
think it would be so painful.

Outside of EngineController (and perhaps supporting classes) we should
continue to have no Phonon includes, with the possible exception of
PhononNamespace which has Phonon's state system that would probably
make sense to switch too (no more rough conversions between different
state systems).

Ian