Major improvements to processing grid8x8 FFT example:

* EMA Filter;
* Debug infrastructure;
* More rendering smoothing all over the place using a coherent noise;
* Autogenerated color gradient with a coherent noise source;
* ...too much to list...

The now in place FFT processing code can be reused to prototype other kind of visualization
on processing on leds with fadecandy boards.

Signed-off-by: Piment Noir Task Force <elecdev@piment-noir.org>