Support straight copy of vertex buffer without transformations

[uyjulian]

Right now, transformations are done to the vertex data buffer:
For positions, the X position is negative
For UV, the V position is inverted (1-v). This may break mirror wrapping mode when the V position is at 0

May I suggest doing these transforms by setting the scale to negative on the Unity Transform component or the TexEnv parameter of Shader instead of the vertex buffer.

Implementing this may also make implementation of #191 easier.

[atteneder]

negative scales are IMO incorrect and IIRC some systems (physics?) do not work that way.

I'd like to look if this can be solved differently first. Do you have a test model you can share?

Probably related to #176