Add support for arbitrary parameters in models

[amisevsk]

Description

Add ability to store arbitrary additional data in a Kitfile's model, e.g.

model:
  name: my-model
  path: ./model.bin
  parameters:
    <any valid yaml>

This comes with some caveats in serialization:

• Numerical fields will be converted to decimal representation, so 0xFF will be come 255, 1.2e+3 will become 1200
• Strings will be serialized ignoring flow/etc.
• Anything yaml-specific (i.e. not included in JSON) is unsupported
• Maps will have their keys sorted alphabetically ({b: b, a: a} -> {a: a, b: b})

The net effect of this is that the unpacked model may have a (superficially) different Kitfile than the original, but both Kitfiles will pack to the same digest.

Linked issues

Closes #366

[gorkem]

Can you fix the build failure

[amisevsk]

Ah, forgot a license header