* 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
* Fix exception in ReagentPrototype
Due to client trying to access concrete implementations of IMetabolizable that are in Content.Server. This fix checks to see if the prototype is being loaded by the client through reflection. I don't want to move the prototype completely into Content.Server since it's useful for the client to view descriptions and values of reagents without needing to send that data from the server.
* Make fix slightly more explicit
Now it will only load the metabolizable when in Robust.Server, instead of it being anything that's not Robust.Client.
* Add IModuleManager and ModuleManager
Provide simple way to check if shared code is being run by the server or the client
* Change ModuleManager implementations to not require assembly name comparison
Now just has ClientModuleManager registered to client, and ServerModuleManager registered to server.
* Change IModuleManager functions to properties
* Fix failing tests.
This was failing because the tests weren't initializing IoC. Simply using RobustUnitTest wasn't enough because that doesn't initialize content either. I did some cleaning up so now content IoC is registered via ContentUnitTest.
