WPF: Fixed bugs in loop playback, can now change loop from ILoopsView.

- Fixed crash bug in WaveFormControl where the scrubbing speeds would
not be initialized correctly.
- Fixed bug in LoopsPresenter where the loop would play instead of
stopping.
- Added IsPlayingLoop property in IPlayer/IPlayerService.
- Fixed loop playback in Player; loops are now playing correctly.
- A little bit of code cleanup in Player (use auto properties when
possible)