Optimizations for led_plaything's usage of PlasmaLayer

Hello,

I adapted PlasmaLayer into C. It works with led_plaything's usage of the PlasmaLayer, however since led_plaything does not pass color into PlasmaLayer, that has not been implemented.

Give me some way to test that and I can add that functionality back in, but for now, it's should be good enough for someone else to easily adapt as needed.

-s