Update io_export_babylon.py

This is PR one in a series for creating an ammojs plugin.

The box and sphere constants were backwards from what I found in the engine so I swapped them 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.
Update babylon.physicsEngine.js
Update babylon.physicsEngine.ts
Update babylon.physicsEngine.js
Merge pull request #231 from shannonmpoole/master

Impostor Constants Update