Create a high-level API that uses midilib's `midibin`for writing directly to MIDI devices

[oubiwann]

This code will ultimately be called by what is created in:

• 56

However, that code will mostly be contributing device and channel for use in these calls; as such, design work can continue in parallel with that work.

This new high-level API will need to:

• create an Erlang MIDI term (midimsg:*)
• encode that term to MIDI binary (midibin:*) -- not term_to_binary
• send that MIDI binary to a MIDI device with um.nif:send

As a high-level API, we'll want to provide more than just a direct, 1:1 mapping to the low-level midimsg:* and midibin:* functions. And we won't want to pass data structures -- we'll want to pass args, as appropriate per function. These two requirements complicate the implementation somewhat.

Tasks:

• [x] Create a core send/3 function that:
  • [x] takes device, channel, and a MIDI message in term format
  • [x] encodes the MIDI message
  • [x] uses um.nif:send to send the binary MIDI message to the given device
• [x] Create a core batch/3 function that:
  • [x] takes device, channel, and a batch MIDI message in term format (list of MIDI messages wrapped in a batch tuple)
  • [x] encodes the MIDI message
  • [x] uses um.nif:send to send the binary MIDI message to the given device
• [ ] Decide upon the optimal manner for all high-level functions of this API to utilise these core functions

[oubiwann]

For the last bullet, I'm experimenting with apply in undermidi.device.conn ...