WPF: Implemented everything in Audio Preferences, plus lots of bug fixes.

- AudioPreferences: Output device and sample rate can now be changed,
and this required many bug fixes throughout presenters and services to
work.
- MainWindow: Fixed several bugs; disabled all controls when the player
is stopped.
- Added Reset method to OutputMeterControl, WaveFormControl and
WaveFormScaleControl.
- Fixed bug in WaveFormScaleControl where the scale would not be updated
when switching to a new song.
- Fixed margins issue in ImageButton.
- Fixed bug in Player where the timer would not be stopped when stopping
the player.