Overcoming image reflections and right hand systems per mesh

[JohnK]

@ecoin

To work with both Babylon created Meshes (UV start from top left) and GLTF (UV starts from bottom left) at the same time

This is not true for Babylon.js see UV Map flipped for Imported Mesh from Blender file.glb - #63 by JohnK

Text reflection can occur if in constructing a mesh uv values are flipped on the faces of the mesh, (u, v) values are still read from the bottom left of the image.