Support defining the studio model from the studio.toml config file

[chris-zen]

This would allow to define the studio configuration from the studio.toml file. It would include which tracks exist, what device chains, sources and destinations, what clips and notes, and sequences of clips.
That task has several motivations:

1. Prepare the terrain for the load/save feature
2. Continue the engine development and experimentation without having a UI
3. Allow for simple use cases, like a VST host for development