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.Game/WorldUtils.cs

@@ -24,7 +24,7 @@ namespace OpenRA
 		public static IEnumerable<Actor> FindUnitsAtMouse(this World world, int2 mouseLocation)
 		{
 			var loc = Game.viewport.ViewToWorldPx(mouseLocation);
-			return FindUnits(world, loc, loc).Where(a => world.LocalShroud.IsVisible(a));
+			return FindUnits(world, loc, loc).Where(a => world.RenderedShroud.IsVisible(a));
 		}
 
 		public static IEnumerable<Actor> FindUnits(this World world, PPos a, PPos b)