New ground cleanup

Fixes #2946
* I cleaned up the meshes, restored the smooth shading. Also I made some geometry optimizations, removed a whole lot of unused materials, and remade the lower LODs by hand to replace those decimated ones (about the same tri count, but better looking this way). 
* I removed the unneeded light tags from the lower res.
* I moved the landing collision meshes to the landing model.
* Adjusted LOD range to 2km.
* Restored the model to 1x scale. All things were parented to a scaled down empty.

I've changed the model file accordingly. I also renamed the .DAEs to .dae, but git restored them to uppercase, so I changed those back in the model file. (reason for two commits). Also the first commit says deleting, but I just confused something, that's why I named it that way. 

There's quite much room for optimization left, and this station desperately needs a proper texture. It's on my list. :D