Shader system update 2

Also note that there is fresnelFactor variable in material now, so needs migration probably.
It works as power for dot(V,N) when using simple fresnel shader (covers most needs) and as IOR using complex shader.
So to use fresnel, one should:

1. Select fresnel mode:
pc.gfx.shaderChunks.defaultFresnel = pc.gfx.shaderChunks.fresnelSimplePS;
or
pc.gfx.shaderChunks.defaultFresnel = pc.gfx.shaderChunks.fresnelComplexPS;
(default is empty string = no fresnel)

2. Set fresnel factor, e.g:
material.fresnelFactor = 1.5;