Add a ship to the asteroid field

[NicholasBatesNZ]

We need to be careful not to go overboard here so perhaps a ship (using the imperialBig or other DestSol ship sprite) that wizzes in and out every now and then shooting asteroids on its way will suffice.
It would also be cool if this ship became 'confused' and stays on the 404 page, perhaps with a "404" on its side.