add Plane.intersectLine with unit tests.
WebGLDeferredRenderer: merged @MPanknin's area lights.

To be continued ...

todo:
- optimize vectors that don't need to be computed in shaders
- use material albedo
- add specular term
- wrapAround lighting (if possible)
- make attenuation parameters uniforms or defines instead of hardcoding them
- this is not using surface normal anywhere, this can't be right?
- maybe some box proxy instead of full-screen quad

See #2624
Merge remote-tracking branch 'remotes/mrdoob/dev' into dev
WebGLDeferredRenderer: optimized area lights computation.

Moved computation of view space position, normal and right vectors out of shader into JS and passing them as per-light uniforms.
WebGLDeferredRenderer: taking into account material color and light intensity for area lights.

Also added forgotten AreaLight.js
WebGLDeferredRenderer: added specular term for area lights.

Using original ArKano22's way:

http://www.gamedev.net/topic/552315-glsl-area-light-implementation/
WebGLDeferredRenderer: more area lights shader optimizations.

Up vector can go outside of the shader. Attenuation can be computed only for lit pixels.

Also removed magic 1.5 constant in diffuse term.
WebGLDeferredRenderer: made attenuation parameters properties of AreaLight instead of hardcoded constants.
Made area lights example a bit more fun.
I tried to replace the box.js with CubeGeometry but I guess material.side is still not implemented.
Cleaned up Camaro example code a bit.
Simplified ui.js.
Simplified ui.js a bit more.
Editor: Simplified layout (thanks to @emackey for teaching me basics of css :P)
Also moved some more ui.js styles to the app's css.
Editor: Removed unneded style.
Added devicePixelRatio to CanvasRenderer and WebGLRenderer.
Updated builds.
Nulling instead of deleting in dispose().
Still waiting for an "official" recommendation from a VM guy though.
Merge remote-tracking branch 'bhouston/vector-index-accessors' into dev
Updated builds.
renderer.devicePixelRatio is now a public property. Fixed SpritePlugin.