Chording Key Capability

[jtgans]

One of the things that was really neat with the scriptability of the G13 drivers was the ability to write an "overlay" or "chording" setup in Lua and then it just sorta-worked, by switching key sub-profiles. It would be neat if we could write something in the driver itself that handles this layering/chording behavior naturally. Effectively making the assigned G key like a momentary M1-M3 key.