CCBReader + CCLightNode - Support for light property animations

- Add CCBActionTweenColor, an internal action for tweening color properties.
- Handle CCLightNode's properties in CCActionManager's actionFromKeyframe0: andKeyframe1: ... method
- Implement copyWithZone: on CCActionTween to fix an exception when chaining tween sequences together. Without this we end up with an uninitialized tween object with a nil property key.
Thanks Martin. I was wondering about this part of this change. @vlidholt and I discussed making this particular class internal to CCBReader for now but it certainly could be made public instead if people would find it useful outside of this context.