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.
What happens when a user has offset mode on, and has pitched a track all the way up, and then they load a new track?  They can only pitch down because the knob is all the way to the right.  We should always reset, and use soft-takeover for users with non-infinity knobs