Include a way to load/save entire sample memory including mapping

[reidevries]

I want to be able to easily backup the entire sample memory and restore it at a later date with the same mapping in one single command. I also want to be able to define new mappings on the computer without having to individually upload samples.

These could both be achieved by for example using a YAML file for defining how sample memory should be arranged, for example:

# classic-drum-machines.yaml
sample_memory:
  001: 909bd.wav
  002: 808bd.wav
  003: 707bd.wav
  ...

Then you could upload it with volsa2-cli restore classic-drum-machines.yaml. Likewise, you could download a sample library from the device with volsa2-cli backup default-volca-samples.yaml.

This would be fairly easy to achieve via scripting so it's not very unix philosophy or whatever but I think there's value in building it directly into the application to make this process more user-friendly. And it's pretty simple so I'll probably just work on it myself.

[reidevries]

Currently working on this, backup is working (although I need to tweak the serialization) restore should be done by the weekend