Updated misc_sound example with same functionality.

Just a single callback is now passed  to loader.load( "scene.js", callbackFinal ) - callback which is called when everything from the scene was already loaded.

If you want to use also callbacks for initialization of procedural synchronously created elements, you can set property of loader:

loader.callbackSync = function( result ) { ... }

If you want to get callback for load progress, set:

loader.callbackProgress = function( progress, result ) { ... }

Also added per scene creation of collision systems (it used to be singleton).

Sound3D ⟶ Sound

Thanks to @mikaelemtinger ;)

- removed unnecessary normal matrix computation in hierarchies (this is already done in renderer)
- removed unnecessary enabling of attribute arrays in every frame (it's enough to do it when shader program is created)
- depth test is now only set if it changed

- 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.

Otherwise things are very much work in progress, expect everything to be broken.

Starting to prepare stuff for adding Fog. Having Fog.js inside /scenes doesn't sound right, but I guess it can be there for now...
The idea would be to do `scene.fog = new THREE.Fog( color, near, far );` This way seems consistent with the rest of the API. By default `scene.fog` is `null`.

Added a check in `Scene` to make sure the avoid duplicate objects.
WebGLRenderer2: In the process of handling > 65535

Not anymore automatic, but also much less wasteful.

Has to be called in tandem with scene object removal:

    scene.removeObject( object );
    webglRenderer.removeObject( scene, object );

 * Add lighting code in the scene rendering loop

- Enabled Scene.removeObject
- Removed computeNormals() from Geometry

+ Workaround for WebKit not supporting rgba() in SVG yet
+ Aesthetic changes on the readme file

Added THREE namespace
Camera.x -> Camera.position.x
Camera.target.x -> Camera.target.position.x
ColorMaterial -> ColorFillMaterial
FaceColorMaterial -> FaceColorFillMaterial
Materials are now multipass (use array)
Added ColorStrokeMaterial and FaceColorStrokeMaterial
geometry.faces.a are now indexes instead of links