Fix docking collisions with big crappy and ground station.

I've extended the collision geometry down the neck of the big_crappy spacestation and up on a diagonal across each of the pads for the placeholder ground station.

Hopefully this should fix the worst of the problems we've been having with this.

Other problems could still remain, docking timeouts leaving ships blocking bays could still occur. Not sure how the AI handles that right now, if at all.