Surge++ COscillatorDisplay color parameterization

[baconpaul]

Right now COscillatorDisplay (that draws the waveforms) hardcodes the colors.

If you look at LayoutEngineControlFactory.cpp you can see a block (search for "COscillatorDisplay") where the element is created by the control factory and an #if 0 surrounds the set colors

So ideally

1. That #if 0 would be removed and the set colors would exist
2. Then the actual widget (in src/common/GUI/COscillatorDIsplay) would use those colors
3. And we would change the colors in the layout to test it

This is a good entry-to-the-codebase issue for S++

[baconpaul]

Re-tooling the S++ plan so closing these issues.