Third cam pan

Makes the topdown view pan instead of tilt, and adds WASD controls to it, by overriding the threejs navigation functions. Also sets the initial topdown offset to be a little closer. I'm not totally sure if this is the way to go, but I think it's a fair start...

Uses virtual-world-framework/vwf#259

 @BrettASwift @eric79 
Remove commented code.