envMap automatic MIP level (HLSL Only)

[shadielhajj]

Changed the envMap cubmap texture type declaration from the obsolete DirectX 9 (2002) syntax to the newer DirectX 11 (2009) syntax.

This requires clients to update the cubemap declaration on their end from
samplerCUBE _Cube;
to
TextureCube _Cube;
SamplerState sampler_Cube;

This allows us to query the TextureCube object for the max Mip Level.

Currently Lygia assumes a default ENVMAP_MAX_MIP_LEVEL of 3, which is:

1. Dependent on the resolution of the texture
2. Very low for typical 2k cubemap textures.

This results in cubemaps not being sufficiently blurred when using rough materials.
The new system is resolution independent and guarantees correct blurring levels.

ENVMAP_MAX_MIP_LEVEL can still be used to override the automatic setting if desired.