Since distribution maps now use PNG

Add the ability to open 8bit PNG's instead of audio files, this is useful for things like playing around with false color paramaters due to reduced processing time
Also reduce some buffer sizes to more sane values

Also made some floating-point math more explicit

Improved commenting in dsp.c
Updated copyright notices
Code tidy up in some parts

Now RGB based instead of HSV based, this also includes a new RGBA compositing function which cleans up the code responsible false color significantly.

Color palettes have also been moved into 1 file instead of 2

This fixes the build.  It looks like the tree was forked during
some incomplete work :(

new dsp code
ngvi test

-cleaning dsp code

-Cleaning pll

-new resample filter
-accept different sampling rates

change -s option

remove bogus 16bit mode
simplify false color computation
clean and indent code