Add names for the unusal spawners. Closes #131

CustomKnight.nbt -> Zombie Knight
Zombie_Fast.nbt -> Rage Zombie
Zombie_Strong.nbt -> Muscular Zombie
Skeleton_Armored_Axe_Iron.nbt, Skeleton_Armored_Sword_Leather.nbt ->
Skeleton Infantry
Skeleton_Armored_Sword_Iron.nbt -> Skeleton Sergeant