Make the model warper write warped mesh data to disk

[adamkewley]

The model warping UI currently performs the mesh warp in-memory for performance reasons (i.e. so that users can move the blending factor slider in the warping UI and get a fast response). However, this means that when the user clicks Warp Model in the UI the resulting model contains InMemoryMeshes that can't be feasily used outside of that particular session of OSC.

So what we need is to:

• Continue performing mesh warps in-memory whenever the user is playing around in the model warping UI (so that they get fast feedback)
• Have a write_meshes_to_disk option in the API that tells the model warper to write the mesh data to disk so that it can be linked by an OpenSim::Mesh rather than an osc::mow::InMemoryMesh
• Make the explicit Warp Model button in the model warping UI use that option, so that the resulting warped model is OpenSim-compatible

[adamkewley]

Waiting on end-user feedback before closing this

[adamkewley]

End-user did not respond after several requests. Assuming this is fine. Will re-open if they come back with problems.