MP campaign additions/fixes:

- Store tab & cargo spawning
- Sub & shuttle lists and level seed box are disabled when a campaign is active.
- Campaign UI is recreated if a new campaign is started while another one is active.

Barotrauma/BarotraumaClient/Source/GUI/GUIDropDown.cs

@@ -142,7 +142,7 @@ namespace Barotrauma
 
         private bool OnClicked(GUIComponent component, object obj)
         {
-            if (wasOpened) return false;
+            if (wasOpened || !Enabled) return false;
             
             wasOpened = true;
             Dropped = !Dropped;