Don't merge yet, still needs testing.

Displacement should be computed in object space (and shouldn't need scaling).

Correct shadow casting still needs a custom depth material but at least shadow receiving should now work with displaced vertices.

This makes it a bit more heavy but saves quite a few varyings, making it possible to handle more lights in ANGLE.

Fixes #2260

Changed LeePerry in CTM example to use normal map shader.

As per discussion in #1207

This is necessary for OpenGL where pow(0,0) is undefined and apparently can be negative, leading to negative specular light (in DirectX you just get zero).

Also refactored a bit regular Phong shader and refreshed Lee-Perry normal map example to be less zombie-like.

Doing normalization of normals / binormals / tangents in fragment shader instead of vertex shader. This seems to help with artefacts appearing in certain models with OpenGL rendering backend.

Also added modulating environment reflection by specular map.

Before lighting was messed up in dynamically generated cube maps.

Dynamic cube maps need to have flip uniforms (flipEnvMap / tFlip) set to 1, static cube maps to -1 (default).

For standard materials this is handled automatically, it's just something to be aware of when using cube maps in custom ShaderMaterials (dynamic and static cube maps have different cube face orientations, dynamic ones are correct, static ones need flipped x-axis in lookup vector).

There is still mystery of disappearing last cube face (negative-Z) and weirdly clipped objects in cars demo (works ok in simpler test).

This feels more intuitive, otherwise ambiently lit textured surfaces look weird.

Turns out I had it right before after all: to get rid of artefacts it should be multiplied by diffuse term (instead of being patched by conditional).

Added generic ShaderPass. Removed SepiaPass, ScreenPass, VignettePass. Added bleachbypass shader. Simplified multi-composer pipeline in postprocessing example.

Added dot screen shader / effect. Extended postprocessing demo. Fixed viewport bug for render targets.

Added alphaTest parameter to base Material plus corresponding shader chunk in standard materials implementation.

This is for having on/off transparency without sorting using threshold value in alpha channel of diffuse texture.

By default it's switched off (alphaTest = 0).

AlphaTest is not yet handled in shadow maps. This would require passing of diffuse texture to depth material in shadow map render step (and more permutations of depth material).

Thanks to @fazeaction for spotting this.