Fixed Impact reducing durability of non-armor equipped blocks
ItemChecks.isArmor should check for custom armors
For consistency with Bukkit, ItemChecks.isPants -> ItemChecks.isLeggings
Restored original behavior of Salvage.isSalvageable
It doesn't check for custom armors, I don't know if it's a bug or not
Added isMinecraftTool and isMinecraftArmor for clarity