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/Signal/ConnectionPanel.cs

@@ -90,6 +90,13 @@ namespace Barotrauma.Items.Components
 
         public override bool Select(Character picker)
         {
+            //attaching wires to items with a body is not allowed
+            //(signal items remove their bodies when attached to a wall)
+            if (item.body != null)
+            {
+                return false;
+            }
+
             user = picker;
             IsActive = true;
             return true;