New way of parsing the VRML, getting actual nodes and properties that are easier to program against.

This PR adds (not full, but reasonable for now) parsing of VRML fields onto their Nodes, so that it easier and faster to create valid THREE.js objects out of it. It also now warns if you have an (unsupported) Background node. This is because I need to do research on how the original Background node behavior can be best implemented. Suggestion are welcome. It used to be more of a graphical thing.