Document and cleanup some decoration code

include/decoration_inventory.h

@@ -11,13 +11,13 @@ extern struct DecorationInventory gDecorationInventories[];
 
 void SetDecorationInventoriesPointers(void);
 void ClearDecorationInventories(void);
-s8 GetFirstEmptyDecorSlot(u8 idx);
+s8 GetFirstEmptyDecorSlot(u8 category);
 u8 CheckHasDecoration(u8);
 u8 DecorationAdd(u8);
 u8 DecorationCheckSpace(u8);
 s8 DecorationRemove(u8);
-void CondenseDecorationCategoryN(u8);
-u8 CountDecorationCategoryN(u8 idx);
-u8 CountDecorations(void);
+void CondenseDecorationsInCategory(u8 category);
+u8 GetNumOwnedDecorationsInCategory(u8 category);
+u8 GetNumOwnedDecorations(void);
 
 #endif // GUARD_DECORATION_INVENTORY_H