<mixer> mixer now inside masters
Add setPitch functions that use PhaseVocoder

These functions allow the pitch of a sound wave to be set with varying
quality.  With a quality of 0 the sound's tempo will be changed when the
pitch is changed.  Above a quality of 0 the PhaseVocoder will be used to
allow for pitch change without an effect on the sound duration.  Right now
this is quite slow, a quality of 1 should be used.
Add function to set sample rate
Add functions for Digital signal processing

I've added a class to compute fft, and a PhaseVocoder.  The PhaseVocoder
uses the fft function to adjust pitch without affecting sound duration.
Revert "<mixer> mixer now inside masters"

This reverts commit 463f39162b63552ef7714322cedda2aa31a0059d.