Summary:
When the ply format looks as follows:
```
comment TextureFile ***.png
element vertex 892
property double x
property double y
property double z
property double nx
property double ny
property double nz
property double texture_u
property double texture_v
```
`MeshPlyFormat` class will read uv from the ply file and read the uv map as commented as TextureFile.
Pull Request resolved: https://github.com/facebookresearch/pytorch3d/pull/1100
Reviewed By: MichaelRamamonjisoa
Differential Revision: D50885176
Pulled By: bottler
fbshipit-source-id: be75b1ec9a17a1ed87dbcf846a9072ea967aec37