V2.0 2023 "Studio" release

The previous version has been used for several years now, but recently it came to light that it didn't cope very well in a situation when there was a MIDI clock running. Originally designed simply to enable MIDI keyboards to be used in place of a Music 4000 keyboard, this wasn't a situation that the firmware had been pitted against. This new version has been reworked to reduce any latency around receiving and processing the MIDI stream, and also attempts to ensure better compatibility with some more esoteric MIDI messages that may be be encountered if plugged into a studio MIDI chain. Feedback is always welcome.