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.
We have 3 different termini in the tooltips
* Pitch (Musical key)
* musical key
* key

Can we settle for one here please?

Also, is SYNC KEY term really correct? We basically match keys so tracks match harmonically just as the tooltip correctly state.