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/Scripting/RASpecialPowers.cs

@@ -25,7 +25,7 @@ namespace OpenRA.Scripting
 				var target = kv.First;
 				var targetCell = kv.Second;
 				var cs = target.Trait<Chronoshiftable>();
-				if (cs.CanChronoshiftTo(target, targetCell, true))
+				if (chronosphere.Owner.Shroud.IsExplored(targetCell) && cs.CanChronoshiftTo(target, targetCell))
 					cs.Teleport(target, targetCell, duration, killCargo,chronosphere);
 			}
 		}