Add tutorial for fitting textured mesh to multi-view images

Summary: Tutorial showing how to create a synthetic dataset by rendering a cow from multiple views, fit a mesh using a differential silhouette renderer, then fit a mesh using an RGB renderer.

Reviewed By: nikhilaravi

Differential Revision: D22513859

fbshipit-source-id: 24bdaac4ebec6dd01f98e2f5c702065f9335ff33

Author: Steve Branson