CCEffectLighting - Cutoff radius, falloff functions, coordinate system issues

- Do light cutoff / falloff math in 2D instead of 3D.
- Add support for non-linear falloff via a 50% intensity radius in addition to the cutoff radius.
- Move all lighting calculations into world space as this makes it easier to handle sprite scaling here (especially non-uniform scale).

Still need to fix the transform matrices so non-uniform scales do not skew the tangent and binormal vectors.