Implement oscillator sync

[timowest]

The UI functionality is already available, but the synth doesn't take it into account yet.

Considerations:

• [x] Increment phase before processing, not after
• [x] When bandlimiting/polybleping normal and sync phase resets need to be treated differently

http://www.cs.cmu.edu/~eli/papers/icmc01-hardsync.pdf http://en.wikipedia.org/wiki/Oscillator_sync#Hard_Sync http://dafx12.york.ac.uk/papers/dafx12_submission_37.pdf Digital Sound Generation - Oscillators http://www.kvraudio.com/forum/printview.php?t=192829&start=0 http://www.native-instruments.com/fileadmin/ni_media/downloads/pdf/SineSync.pdf