Specular map works like it used to for normal map shader. It is assumed to be a grayscale texture.

For Phong specular map value modulates specular term strength and environment map reflection strength.

For Lambert and Basic materials specular map affects just environment map reflection strength (as these have no specular term).

Still not very sure how environment mapping and specular term should interact with each other.

Changed vertexColor default from "false" to "THREE.NoColor" constant. Added missing morphNormals parameter to ShaderMaterial.

Moved materials/RenderTarget.js ⟶ renderer/WebGLRenderTarget.js

CanvasRenderer: Hocked materials linecap/linejoin/wireframeLinecap/wireframeLinejoin with context.linecap/linejoin. Made it 'round','round' by default again.

Work in progress, not expected to work yet.

(among other things, we don't deal yet with new vertex colors for particles/line/ribbons, for the moment they just use geometry.colors as before, also we need to specify which type of uvs to use somewhere, analogous to which type of vertex colors to use)

Refactored everything to use CamelCase naming for properties. Plus some smaller fixes here and there.

Went through all examples, all should work.

JSON files exported from Blender / converted from OBJ files still use underscored property names internally. I don't know, should these also be changed?

I don't remember when was the last time I used them. Current Web Developer Tools do this already for you.

Color::updateRGBA ⟶ Color::updateRGB

- getters/setters are no more in Vector3
  - object hierarchies thus don't use "isDirty"
  - this was completely killing performance for anything that was touching a lot of Vector3 like creation of meshes and dynamic buffers
  - even without this, performance of hierarchies went up (a lot)

- objects do not get passed renderer anymore
  - camera was almost also removed, but this is useful for LOD (though there may be some cleaner way to do this?)

- material ids are now unified, this makes "geometry.sortFacesByMaterial" faster (thus scene init / GUI blocking is shorter)

- all WebGL examples should work now (render-to-texture has weird lights and in some camera control feels different)

- CanvasRender still broken, despite many efforts :(
   - currently only points and lines work, faces don't show up. I think this may need assistance from mrdoob.

This is to be able to control depth buffer writing / testing on per geometry chunk level (before it was possible just to hack it on per scene level via exposed GL context).

Disabling depth test is useful for example for additively blended particles, handling of transparency or for having background textured quad.

Another option would be to have it on per object level, but then this could prevent different handling of objects with both transparent and opaque parts.

Also in this commit:

- more progress towards mesh vertex colors
- less matrix multiplications in render call
- fixed ugly bug in doubleSided / flipSided handling
- cleanup of materials
    - added a lot of missing stuff in debug strings and parameters handlers
    - normal and depth materials now have opacity parameter
    - wrote comments for non-obvious things

Work in progress ...

Cleaned up shader snippets in WebGLRenderer2.

Made 0xffffff the default color on all materials (0xeeeeee was making the AO a bit darker).

Fixed SVGRenderer.

Added refractive mapping and mixing combination mode for the environment map and the underlying material.

This commit has handful of things going on:

- had to sacrifice one light to please ANGLE, making it again up to 4 instead of up to 5 total lights :(

- Basic / Lambert / Phong materials now have new parameters:

    "combine": THREE.Mix | THREE.Multiply [default]

      - tells how to combine environment map with the original material:

         - "Multiply" creates chrome-like metallic look (it's what was already there),
           color of the underlying material is multiplied with the environment map,
           this creates different colored metals

         - "Mix" creates shiny plastic look
            color of the underlying material is lerped with the environment map,
            amount of the contribution from the environment map is controlled
            by another new parameter "reflectivity"

    "reflectivity": <float> [from <0.0, 1.0>]

       - controls mixing of underlying material and environment map for "Mix" combine mode
          0: pure underlying material, zero contribution from environment map (Basic/Lambert/Phong)
          1: pure environment map, zero contribution from underlying material (uncolored chrome look)

    "refraction_ratio": <float>

      - controls refractive mapping, ratio of the index of refraction in the medium containing the incident ray
        to that of the medium being entered
      - sensible values seem to be from ~0.6 - 1.0
        (in theory, e.g. air/glass should be 0.75, but this looks weird, values between 0.9 - 1.0 give the most interesting results,
         though maybe there is bug somewhere in my code)

      - for use refraction mapping, just add parameter to TextureCube like this (default is reflection mapping)

          "new THREE.TextureCube( images, THREE.RefractionMap )"

Cleaned up the escher cubemap code a bit. Also, I think it looks much nicer without illumination... ?
At first I though the cube around the sphere was x-inverted (unless the in tention is to simulate refraction...) I've tried changing that but the effect is still weird. I guess those textures work mainly for the sphere and not for the panorama.

I reused the code and did another example using the skymap. More to come ;)

I can see some lines at the edges of the planes though. I guess that's antialiasing kicking in. Should be fixed with a proper cube mesh I guess.

CanvasRenderer has a property called `autoClear` which is true by default. By making it false you have control of when the renderer cleans the screen (by calling renderer.clear()). I wonder if something like that can be added to the WebGLRenderer? That way we can render the cube outside the spheres from a diferent camera (centered in the middle of the screen) than the spheres floating.

Also, added `shading` parameter to `MeshBasicMaterial` (environment mapping was being rendered faceted when using `MeshBasicMaterial` because `shading` was missing (and thus Faceted)).

TODO:

  - maybe image array loader should go into TextureCube.js so that people could just reuse the code

  - it may be worth to be able to specify different combination of environment map and underlying material (in single render pass),
    currently color/color map/environment map are multiplied, though addition also produces very interesting looking materials

GouraudShading and PhongShading ⟶ SmoothShading

Not all features from the new material format are implemented yet, though already now it's more powerful than the old format (you can now use  texture also in Basic and Phong materials).

Also started to retire old model format: removed old OBJ converter and meshes that it generated.

TODO:
 - take into account shading and blending parameters
 - transplant cube map support from experimental material

Almost done porting CanvasRenderer to the new material system (plus some performance gains on the way :D)
`Color` now handles hex with no alpha byte (probably there is a nicer way of doing it...)

Experimenting with different syntax for materials (just hex instead of THREE.Color in API), checking how it feels with shaders example.