SGModel ground and orbiting stations

# Description.
LmrModel is on the way out, so here's two of the station models converted to work with SGModel complete with collision meshes. Name "big_crappy" and "ground_station_4".

As a bonus I've also disabled all of the other existing stations. "nice" and "hoop" had to go because of the insane, reality defying, docking and undocking procedures which involve bits of the station actually appearing and disappearing. All of the other were disabled due to them having less than 4 ports and because I couldn't be bothered to spend all my weekend converting them!

# Testing Notes.
I've tested this as best I can however I think that the "ground_station_4" model could do with some manual landing testing. 

"big_crappy" should be ok as I got it working with manual docking before I got the autopilot docking to work :)

# LMR to SGModel notes.
The hardest parts of all this were as follows:
* Placing the pad collision geometry to match the scripted docking anim waypoints, one is text the other is visual. Needs some refinement, making them named points like "docking_stage_X" perhaps.
* Materials, LMR models for the ground and orbiting stations have a lot of materials, a lot of little textures, and are a big pain in the arse!
* The SGModel parser error output wasn't obvious when I'd cocked something up or when a model or mesh was missing. Not sure what to do about this but more detailed output would be nice.

# In closing.
We need a few SGModel ships, then LMR can be disabled.

Andy (aka @FluffyFreak)