SubstractiveBlending ⟶ SubtractiveBlending

Implemented material blendings (THREE.NormalBlending, THREE.AdditiveBlending, THREE.SubtractiveBlending) in CanvasRenderer
Added MeshNormalMaterial (per face)

Cleaned up CanvasRenderer and SVGRenderer code a bit.

It's commented out, as it breaks shader validation in current Chrome :(.

There seems to be some bug in Chrome / ANGLE making it barf when using "gl_FragCoord" in fragment shader.

Curiously, while it breaks both 9.0.576.0 dev channel and latest continuous build 9.0.583.0, it does work fine in canary build with the same version as dev channel (9.0.576.0).

Go figure. Also in Firefox 4 beta 7 it works fine.

It seems there were some recent changes in handling of "gl_FragCoord" on Windows which probably broke something when fixing other bug:

http://code.google.com/p/chromium/issues/detail?id=59762
http://code.google.com/p/angleproject/issues/detail?id=71

TODO: make isolated test case and submit bug report (if this doesn't go away in next Chrome update).

Have to commit broken build (missing MeshDepthMaterial.js) as git doesn't want to proceed with new merge till the old one is not committed :(

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

Optimised Particles projection in CanvasRenderer.

Most of the examples working.

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.

First attempt at MeshBasicMaterial / MeshLambertMaterial / MeshPhongMaterial. Also: testing branching :)

This is not supposed to work yet, all is in the flux, do not base any code on this.

* THREE.Rectangle: `_x1`, ` _x2`, `_y1`, `_y2` ⟶ `_left`, `_right`, `_top`, `_bottom`