dmxgus: Add comparison MID generator script.
dmxgus: Add comparison MID generator script.

This script generates a MIDI file that plays all of the comparison
groups from config.py. This allows instruments to be compared, so
that similar-sounding instruments can be grouped together.

CWolfRU/freedoom,jmtd/freedoom,jmtd/freedoom,CWolfRU/freedoom,jmtd/freedoom