Terminate application after window close

src/Gui/Gui.cs

@@ -42,6 +42,12 @@ namespace WorldOfPeacecraft
             this.PerformLayout();
 		}
 
+		protected override void OnClosing (System.ComponentModel.CancelEventArgs e)
+		{
+			base.OnClosing (e);
+			Backend.Stop ();
+		}
+
 		public void DoPaint (object source, PaintEventArgs args)
 		{
 			BufferedGraphics buffer = BufferedGraphicsManager.Current.Allocate (Board.CreateGraphics (), Board.DisplayRectangle);