Progress on multiplayer campaign:

- Moved SaveUtils to the shared project.
- Moved the "new game"/"load game" menu logic to a separate class.
- Somewhat functional campaign UI in the server lobby (only the map view is usable atm though).

Barotrauma/BarotraumaClient/Source/GameSession/GameModes/SinglePlayerCampaign.cs

@@ -344,7 +344,7 @@ namespace Barotrauma
 
         public override void Save(XElement element)
         {
-            XElement modeElement = new XElement("gamemode");
+            XElement modeElement = new XElement("SinglePlayerCampaign");
             
             modeElement.Add(new XAttribute("money", Money));