Batching plans

[ncannasse]

In order to improve batching of similar meshes, a step by step approach seems interesting:

• Create a Batcher prefab that auto batches its children (recursively) checking for eventual shader/material to ensure they can still apply - and skipping single instance meshes ?
• Have Meshspray inherit this prefab
• Create MeshLibrary that from a children list of meshes will generate a single hmd and texture data with different materials (one per mesh)
• Allows to set a MeshLibrary generated hmd to Batcher in order to use single draw call instancing for all sub meshes. Deal with material props.
• Allows to turn Batcher in Dynamic mode, which would capture children emit() calls recursively then either let them pass (shader applied) or emit instances dynamically (with cache).

[ncannasse]

Partial implementation has been made, further dev will be handled in #213