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.
The problem is the word "scale" can refer to a musical scale, so this may be confusing to English speakers.  Maybe we can flip it around:
"Lock to original key (offset range)"
"Lock to current key (absolute range)"