Matrix4.lookAt(): y doesn't need to be normalized because it's a cross product of 2 normalized vectors

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

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

Changed console error to return null and updated WebGLRenderer to handle null value. A valid matrix with no rotation and 0 scale will have a 0  determinant and does not need a normal matrix.

Work By: Erik Kitson

Fixed typos in Matrix4's transpose() and getInverse(). Also added convenience functions for adding a translation or rotation to a matrix (rather than just setting them).

Work by: Erik Kitson and Khang Duong

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... ).

This buggy pattern ("something = parameter || nonzero value") exists at more places though elsewhere setting to zero doesn't make that much sense (e.g. in geometries).

Not sure if we should change it everywhere to proper pattern ("something = ( parameter !== undefined ) ? parameter : value").

Maybe it would be good for establishing habit. I remember fixing this buggy pattern long ago but it just keeps popping up.

Still not very fond of decompose returning new array. We will see when it'll be actually used - as API allows for passing in existing translation, rotation, scale, maybe this return array could be eliminated.

(per Qt API design suggestions http://developer.qt.nokia.com/wiki/API_Design_Principles)

Also some more whitespace cleanup.

Added functions for getPosition(), getColumnX(), getColumnY() and getColumnZ() to easier access the different components of the matrix.

Gah, that was painful. Obvious solution with object.lookAt doesn't work, forward facing direction (heading and attitude) is fine, but banking gets messed up:( Tried many fixes, none worked, so I just resorted to simple rotation around Y-axis based on direction vector.

Added translate( distance, axis ), translateX( distance ), translateY( distance ) and translateZ( distance ) methods to Object3D.
Camera3D translate method overrides Object3D's one. NoFly parameter removed (this should be handled from outside I think).

Object3D::lookAt works! (and Vector3.setRotationFromMatrix too!)

Next: Object3D::translate...

Animation.js - fixed scale bugs and removed flattenToArrayOffset
AnimationHandler.js - fixed so keyframes at same time is removed
Matrix4.lookAt - fixed so it handles situations where z === up and where eye === target
SkinnedMesh.update - added flattenToArrayOffset in end of update

Minor tweaks.

- Wrong in last commit, now the inversion of position is removed