Changed WebGLRenderer to use 3x3 normal matrix.

Limitations of WebGL lights:

- currently handles only single one of each ambient/directional/point light
- light intensity modifier not yet taken into account
- only diffuse term (this applies also in CanvasRenderer)

Extended CanvasRenderer to be able to handle decals (MeshBitmapUVMappingMaterials as secondary materials).

For decals you need to set "decalIndex" property of the material (corresponding to materials index of the original mesh UV material).

Added multimaterials example.

Fixed forgotten sphere smoothing in OBJ converter example.

Added OBJ converter test example.

Modified Three.js to handle converted models:

 - extended WebGL renderer to use texturing
   - broke down model into multiple VBOs according to materials
   - textures are lazy created when images get loaded
     (converter takes care of resizing images to nearest power of 2
      dimensions using 2d canvas)

 - changed material array semantics in Mesh object
    - before: multiple materials were applied to all faces (broken in WebGL, needs multitexturing shader)
    - now: there is only single material per face, but one mesh can have faces with different materials

 - added per vertex normals (to get smooth shading in WebGL)