Collaboration with Hexter author to provide real time control over Frequency Coarse parameter

It is now possible to control the ‘Frequency Coarse’ paramater of all six ‘DX7’ FM operators in real time, thanks to some additional code kindly provided by Sean Bolton. It was previously possible to modify the parameters, but only using a sysex message that would affect the following note (a limitation present for many parameter changes on the original hardware DX7). Real time control of FC is now possible using MIDI control change messages. The implication of this is that any physical controller (modulation wheel, data slider) can be mapped to control these parameters.