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.
in the future, it's easier for me to review the PR if there is one feature per PR.  This is very large and contains more than one new feature so it's tricky to review.  Anyway it's not a problem, it just takes longer