Define LFE/Erlang wrapper API

[oubiwann]

For examples of how the NIF is used in gen_servers:

• tau_server/tau_server_midi_in.erl
• tau_server/tau_server_midi_out.erl
• tau_server/tau_server_midi.erl

For low-level APIs:

• [x] Wrap the Erlang NIF module using Lispy names with no duplication (what is called "stuttering" in the world of Go ...)
• [x] Move NIF wrapper from sp-midi toms.nif
• [x] https://github.com/erlsci/midilib/issues/7

For high-level APIs:

• [ ] ❌ Maintain API compatibility with the Go midiserver (see undermidi/go/execserver.lfe)
• [ ] ❌ Support the calls made from undermidi (see undermidi/supervisor.lfe)
• [x] #57
• [x] #56
• [x] Write/update a high-level API that wraps the above two (e.g., for things like "play chords", "repeat sequence", etc.)
  • [x] for all calls, support passing device and channel as well as no device and channel (only both or only none)
  • [x] for each call, determine if it's best to use the send functions or the batch functions

[oubiwann]

With the use of Sonic Pi's MIDI Erlang NIF, we no longer need to run a process that communicates with the OS' MIDI system. That server completely goes away.

We're also going to do a pretty significant refactor of the undermidi API to a few things:

• Clearly separate out what is a MIDI wrapper, and
• What is undermidi-specific, custom, composed MIDI calls, and other such functions

For this new design (and to a certain extent, architecture) in undermidi, see the dedicated ticket:

• 56

[oubiwann]

We're creating the API as we go, and have found a good approach for now. Going to close this. Will create a new ticket if the current approach ends up needing a re-think.