Pitch scale

This is the fist chunk of commits, that fixes the scale jump issue of the pitch knob. 
https://bugs.launchpad.net/mixxx/+bug/1258617
The code is still a bit ugly because it still uses the old pitch adjust CO internally but it works. 
I am working on a solution where we just pass pitch and tempo to the scalers, which will clean up the code.
can you make sure you are using the exact same algorithm to pick a sync target as master sync does?  (Obviously the internal clock doesn't have a key, but there is pickSyncTarget logic in there and we want to make sure it's the same.)

We want to make sure that when a user presses the sync button and then a key sync button, mixxx chooses the same track for both operations