Omnibus PR: MI-Engine engines, softcut tweaks, and new scale degree operator

[eethann]

This is a lazy omnibus PR with changes from my personal fork. Feel free to request I split it into separate PRs, I understand this is not best practice.

This PR includes:

1. Mostly engine integrations for the MI engines, along with README updates for each.
2. An operator I've gotten a lot of use out of, basically a fork of the rnote op that takes a scale, base octave, scale degree, and root note, and outputs a octave note cells below it for use in MIDI and synth ops. I've found this extremely useful in making generative melodies, etc.
3. Some tweaks to softcut for panning, based on a discussion in the softcut library thread on llllllll.co

Thanks!