Talking with Emilian about this commit, we came to the conclusion we don't want share uniform between .eff file
This reverts commit 91a6a27f32ee5f79e1d7e0d4570e879a902de58f.
The overriding of the color mode uniform in the default model effect
wasn't working. It's difficult to override the individual properties
of techniques, especially if their names aren't unique. So, I changed
the model-default effect to use a parameter for the color-mode
uniform; material-off.eff and material-diffuse.eff override that.
Use two-pass rendering for some shaders to reduce the cost of expensive shaders.
Implement some material animations using a shader uniform.
Eliminate use of gl_FrontFacing. It's too buggy on ATI/ Macintosh.
