changed ColladaLoader.js

added an option to use the ambient light in the dae file. I thought this makes sense because you mostly want to have only the scene and not another AmbientLight in your Three.Scene, even if it is black. it just spams the sceneGraph.

marked an unused function with a comment ;) 

Also added another condition for the getChildByID condition because using the latest ColladaMax Loader, node names and visualScene object.ids are not identical and have a "node-" prefix

other changes according to: 

https://github.com/mrdoob/three.js/issues/3995

This is my first PR. Hope everything is ok, my dev branch should be up to date and stuff^^
I tried the 2 collada examples with r63Dev and they both worked as usual.