Impostor Constants Update

This is PR one in a series for creating an ammojs plugin.

The exporter box and sphere constants were backwards from what I found in the engine so I swapped them in the here.

I also want to eventually read from the BGE values as well but that looks fairly involved so I will save that for some other time.

More to come as soon as I can find the time to do a bit more testing on the plugin itself.