Create a comprehensive data-model

[Silvanoc]

Description

Create a data model that completely and consistently documents the resources, objects, data types,... involved in Margo.

Motivation

Set the foundation to address #149

Proposed Solution (optional)

Use LinkML to create the data model. Reasons for the proposal are:

1. Textual-based model that can be easily versioned, compared, edited,...
2. Very powerful and extensive modeling possibilities (inheritance, semantics, loose relationships, references/inlining,...).
3. Powerful tooling with multiple generators (JSON-Schema for data, HTML, Class-diagrams,...).