"Fixed typos in Matrix4's transpose() and getInverse()"

https://github.com/AddictArts/three.js/commit/62d2560b3c7b9868fc25f628c4022448aaff6b00

Bad things (and hard to debug) can happen that affect Ray.

And still readable code...

It's enough to clone just for hits, no need to do it for every face.

Removed some clone() calls while still keeping the code somewhat pretty.

https://github.com/mrdoob/three.js/pull/689

Actually, this would break cameras added as childs of objects, reverting.
So there is no clear and simple way to handling multiple scenes unfortunatelly.
Encouraging `scene.add( camera )` seems like the right thing to do then, less problems.

Actually, I think this can be handled magically instead of requiring understanding of the concept that the camera is part of the scenegraph.
While I was at it, I fixed it so you can use a camera for rendering different scenes (the renderer will add it and remove from each scene graph)	.

It's going to be handy for the WebGLRenderer (__webglObjects)

I had to resurrect parts of old code (keeping track of scene graph changes).

Good news: performance is great, new scene graph gains compound with buffers optimizations and non-array materials refactoring. Together we gained about 15% for rotating cubes performance test (pushing max to 2650 cubes at 60 fps).

Still broken with new scene graph: lod, skinning, collisions, AnaglyphWebGLRenderer, ParallaxBarrierWebGLRenderer, multi-canvas circle example.

Also moved `.overdraw` to Material.
Code is much simpler now :)

Do not use for anything, this is just snapshot of a test in progress. I solved quite a few issues, but many things are still clumsy and broken.

Lots of code got cleaner with seconds, seems we used them before all around.

Also changed examples that didn't need deltas to simple Date.now() plus some more examples cleaning, trying to get rid of obsolescence warnings.

Always use shortest path for Quaternion.slerp (also see: http://www.euclideanspace.com/maths/algebra/realNormedAlgebra/quaternions/slerp/ Other Issues, Inverting Quaternions)

Got tired of redoing deltas all the time. Not sure about API or implementation details, but so far seems to be useful.

In future, we could for example have clocks that are slower / faster than realtime, or fixed step based.

Do not merge, this is very experimental, not sure about correctness, also tons of unsolved things.

Maybe a bit too early, but just want to see that code clean and simple...

* The new system allow us to add lights and cameras as children of any object without hacks.
* The Camera needs to be added to a Scene. If the Camera has no parent it's added to the Scene being renderer automatically.
* I'll work on implementing this into the WebGLRenderrer tomorrow (gonna be a looong day... ).

Now `Camera` can use inherited `update()`