[Bug Fix] Disallow multiple augments in same item. (#1916)

- Disallows multiple augments via #augmentitem or otherwise.
- Added ItemInstance::ContainsAugmentByID(item_id) helper method for finding an augment in an item instance.

common/emu_constants.h

@@ -381,4 +381,11 @@ enum Invisibility : uint8 {
 	Special = 255
 };
 
+enum AugmentActions : int {
+	Insert,
+	Remove,
+	Swap,
+	Destroy
+};
+
 #endif /*COMMON_EMU_CONSTANTS_H*/