Small number of tweaks and fixes to follow up v1.1's release.

• Restored the Plasma Trooper's height to the vanilla Imp's
• Restored the Laser Gunner's height to the vanilla Hellknight's
• Reverted some test nerfs to the tanks' weakness to rockets that were accidentally left in
• Raised the chance for the Nailgun to replace the Rifle from 25% to 50%
• Added a ~10% chance for the Nailgunner to drop the Nailgun itself