MIDI color oscillator overrides

Frequency AND amplitude, for each color component (HLS), for both foreground and background color is 2 * 3 * 2 = 12 knobs. It turns out to be too much to handle live. Better to control the frequencies only, and hard-code the amplitudes:

                amp     freq (range)
color speed     1       .1
lightness       .25     .1
saturation      .5      .1
bk hue          180     .01
bk lightness    .25     .1
bk saturation   .5      .1