Introducing per-player shrouds.

- Each player has their own shroud and their visibility does not extend outside of the shroud. 
- Units and buildings can no longer target other units outside of their visibility. Buildings can still be targetted if they have been explored.
- GPS will provide visibility in the fog-of-war.
- Spies that infiltrate radar domes will gain their victim's exploration and reset it on all clients (if the victim does not have GPS)

OpenRA.Mods.RA/PlayerExts.cs

@@ -0,0 +1,25 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2011 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.RA
+{
+	public static class PlayerExts
+	{
+		public static bool HasFogVisibility( this Player a )
+		{
+		    var gpsWatcher = a.PlayerActor.TraitOrDefault<GpsWatcher>();
+			return gpsWatcher != null && (gpsWatcher.Granted || gpsWatcher.GrantedAllies);
+		}
+
+	}
+}