Editor comes together

The editor is coming along slowly but nicely. I split off the floor structure to a separate ObjC class. The reasoning is that it's easier to handle that sort of ever-changing data in a native environment without always having to bridge across to the more "frozen" LevelFloor class in C++. Instead, I let the editor work on a malleable EditableFloor class, and then insert the (validated) parts into the BaseLevel when I need to run or display it.

Wow, what a coding spree. I'ts 5AM, and I've got the editor to a point where it can (roughly) create linked polygons! Sleep madness!