discord 3.1.0 released, backward compatible

While this release adds new features it is still backwards compatible. Old scripts will run without any modification.

Add -l/--listfile option that allows multiple scripts to be run from a file simultaneously. They can also be run by putting them all on the command line. Options from files in a listfile (has a chorus suffix) are not read, only the play sequences.

Add -s/--shift option. This allows all beat voice carriers and beats to be shifted up or down in synchrony. From just more than -100 to any reasonable positive percentage.

Add a silence voice to serve as a placeholder in scripts, for voices or for time synchronization between scripts.

Changed all the included sound samples to mono wav files from aiff.

Some internal upkeep and tweaking.