Some fixes to attachable items (buttons, signal items, etc):

- Syncing the attached/detached state of the items. This should fix the "received a position update for an item with no physics body " errors: midround-joining clients didn't get notified if an item had been detached, causing the error to appear every time it receives a position update.
- Detached items can be picked up just like any other item, instead of having to use a wrench and wait for the item to "detach".
- Wires can't be connected to items with a physics body (such as detached buttons).

Barotrauma/Source/Items/Components/ItemComponent.cs

@@ -153,13 +153,13 @@ namespace Barotrauma.Items.Components
         public InputType PickKey
         {
             get;
-            private set;
+            protected set;
         }
 
         public InputType SelectKey
         {
             get;
-            private set;
+            protected set;
         }
 
         [HasDefaultValue(false, false)]