Inventory: remove a bunch of crap from interface

some of these (notably the on* methods) are internal and shouldn't be exposed via interface (same crap as Plugin->onEnable() onDisable() etc) and the rest of the stuff is entirely unused.

src/pocketmine/inventory/ArmorInventory.php

@@ -50,10 +50,6 @@ class ArmorInventory extends BaseInventory{
 		return $this->holder;
 	}
 
-	public function getName() : string{
-		return "Armor";
-	}
-
 	public function getDefaultSize() : int{
 		return 4;
 	}