CSG static model rendering

[guusw]

The shapes/operations defined by the shards (#455) need to be evaluated on the GPU, raymarching the result for now.

• [ ] We should try use the existing shader translator to take a shards definition an render it
• [ ] Add some kind of root shard (CSGModel, Model) that contains the list of shapes/operation inside it, the output is a Drawable that can be passed to the renderer