Add quantizer generator support

[oubiwann]

This will allow users to emulate this type of modular synth hardware:

• https://www.youtube.com/watch?v=xnUFtQC0nks
• https://ornament-and-cri.me/

(thanks to @brianstarke for the links!)

Depends on:

• Add rand support in gen_server #114
• Exploration: Use 2 dimensional data as source for music generation  #110
• Implement a random walk scan through noise data lfex/loise#53
• Add "linear scan" function lfex/loise#54
• Add support for finite data traversals lfex/loise#60
• Add support for infinite data traversals lfex/loise#65

Tasks:

• Add rand-note function
  • gets next random number from stateful random generator (see Add rand support in gen_server #114)
  • with appropriate max value (e.g., 127)
  • optionally filter it
• Add filters supporting
  • musical key
  • musical key and scale
  • upper and lower bounds
  • an explicit set of notes
• Implement core concepts in undertone (borrowing implementation ideas from Extempore)
  • Add LFE implementations for keys #116
  • Add LFE implementation for scales #117
  • Add LFE implementation for modes #118
  • notes