Testing the impact of normalization of transformed normals in vertex shaders (phong, normal, normalmap, skin simple).

It seems the effects on performance are minimal: in several random examples it's either not measurable, or just a tiny bit worse.

See #2613

Fixed implications of new MeshFaceMaterial.materials at multiple places (Ray, Projector, ShadowMapPlugin, DepthPassPlugin).

Thanks to @WestLangley for vigilance (see #2623).

Patch to #2623

I believe this is not needed anymore.

Also for the moment in depth pass skipping all ParticleSystems without custom depth material. Otherwise there are GL errors, need to create a proper generic depth material for particles.

See discussion at https://github.com/alteredq/three.js/commit/5cb715520806a5afa1057a31a6777c2e454eeff0

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

Fixes #1805 and #2615 (related already fixed #998).

See discussion in #2613

Finally I just left it behind a flag. I was not able to get as good results for TextGeometry as with unweighted method and split materials for side and front faces.

I wonder how I got that nice look as in screenshot I posted in the issue. It still does look better with weighted than unweighted but nowhere so close as in that screenshot. Either I did some mistake when testing before or there is some bug in implementation now.

See #2610

Small fix to #2610

Because that's what it is.

Now it should look the same no matter where the object is located.

In the process found some issues:

- HemisphereLight shading is wrong for objects not in origin, it shouldn't depend on light position amplitude and object position in the scene
- GL errors about uniforms thrown when all lights have "visible = false"
- object dragging in the viewport sometimes hits invisible wall (I guess it's because of limited picking plane size?)
- ArrowHelper doesn't seem to work for (0,-1,0) direction

Adding Kaleidoscope, Mirror and RGBShift Shaders.

I wonder how this could happen, built lib from that commit does have corresponding change.

Also fixed spotlights shading in Lambert material and light helpers init colors for light intensities > 1.

Please disregard init scene lighting weirdness, this is just temporary, to be able to test light helpers.

Values needed to be divided by 255.