Inventory Input (#503)

* Create ItemSlotButton

* Refactor inventory buttons

Refactor so that KeyBind handling of inventory and hands are the same.

* Refactor InventoryInterfaceController to call ItemSlotManager with entities

This change allows HandsGUI and InventoryInterfaceController to just call ItemSlotManager.OnButtonPressed with an entity instead of a slot.

* Add CooldownCircle to ItemSlotButton

This allows Hands and Inventory to have cooldown circles on their ItemSlots.

* Refactor HandsGUI to use ItemSlots

This allows functionality and GUI to be the same between Inventory and Hands.

Added clicking empty hand to switch ActiveHand to clicked hand.

* Implement CooldownCircle in ItemSlotManager

Reorganize files

Content.Client/EntryPoint.cs

@@ -215,6 +215,7 @@ namespace Content.Client
             IoCManager.Resolve<IChatManager>().Initialize();
             IoCManager.Resolve<ISandboxManager>().Initialize();
             IoCManager.Resolve<IClientPreferencesManager>().Initialize();
+            IoCManager.Resolve<IItemSlotManager>().Initialize();
         }
 
         public override void Update(ModUpdateLevel level, FrameEventArgs frameEventArgs)