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 
I think the amount of params here is absurd, but apart from wrapping them in an array/object or doing a `get/gotProperty` on them from the `navObject` id (which I think should be kept in the core), I am not sure what to do about them.