Feature Request: Choke groups

[robelanator]

It would be great if you could add choke groups to Geonkick. For grouping open and closed hi hats, for example. Or multiple variations of a ride cymbal.

[iurienistor]

@robelanator Hi, yes, it would be a good idea, but there is a need to modify some things in the core synth. Thus, I'll put this PR for the future.