gradient util, started waterfall implementation
Waterfall now being displayed 2048x512

Uses indexed color scheme, FFT image is byte array
waterfall optimize, fm demod audio filtering

Moved waterfall increment into rendering to reduce audio processing
impact.

Added another test filter and resample stage to FM demod experiment to
clean up audio and remove high pitch on stereo channels until it can be
demodulated.
Waterfall tweaking, automatic range adjustment
FM Demodulator fixes

was an implicit float to int in the primary filter cutoff value causing
distortion.
Separate Primary GL Context and visuals canvas

Can now create multiple GL canvases with shared context
Separate visual components Scope/Spectrum/Waterfall

Each now on it's own canvas with shared GL Context
Merge pull request #3 from cjcliffe/the_waterfall

Addition of waterfall and separation of visual components