Add psychoacoustic bass enhancer EEL program

[44100hertz]

All this does is low pass the source signal to split it into low and high parts, saturate the lower part of the signal, and then blend that with the high part.

This increases the perceived bass response of the device without increasing the actual bass level; a strategy commonly used in laptops, phones, and BT speakers.

Needs further testing and maybe enhancement, but I think it's a good example and fairly useful in its current state.