iOS: Added sliding effect + song position in WaveFormControl scrollbar.

- WaveFormControl: Added sliding effect to scroll bar when zoom is
between 100% and 200%. This makes the scroll bar appearance much
smoother when zooming in/out with touch input. Also added song position
in the scrollbar, so it is much easier to know what the song position is
vs the currently visible area of the wave form.
- Updated iOS project after changes in ISyncView.