Round-robin voice assignement in duo and poly modes

[thomasemilhansen]

Hi all, I implemented round-robin voice assignment in duo and poly modes. Currently voices are assigned from low to high (lowest free voice is assigned on key down). In round-robin mode they are cycled (next free voice is assigned on key down). This opens up for some interesting patches a la MonoPoly and Vermona Perfourmer. I made it so that it's possible to switch between the two modes, using midi channel 3 notes C and D respectively in the configuration menu. I'm new to open source software and unsure how to propose this feature using pull requests. If you want this feature added to the firmware please advise and I will happily share it with everybody.

[xustafu]

Great stuff! Created branch #RoundRobin so you can do a PR so we all can take a look. Thanks a bunch! in advance :)