Craters generate rocky rubble

Hope this works
Fixes infini-bashing metal fence posts.
Fixes a typo.
Merge branch 'Crater' of https://github.com/Mshock777/Cataclysm-DDA into merge2
Merge branch 'fencepost-fix' of https://github.com/Rivet-the-Zombie/Cataclysm-DDA into merge2
Merge branch 'typo-fix' of https://github.com/Rivet-the-Zombie/Cataclysm-DDA into merge2