Create a set of classes used to manage 3d model loading:
- Model: a 3D model composed of multiple ModelMesh
- ModelMesh: a mesh that is part of a Model
- ModelMeshPart: a ModelMesh is split into multiple ModelMeshPart objects, typically based on material information.

Create a set of classes used to manage a collection of ModelMesh, ModelMeshPart...
- ModelMeshCollection, ModelMeshPartCollection...

Create the reader to load a model from file