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/Harvester.cs

@@ -428,7 +428,7 @@ namespace OpenRA.Mods.RA
 			public bool CanTargetLocation(Actor self, CPos location, List<Actor> actorsAtLocation, bool forceAttack, bool forceQueued, ref string cursor)
 			{
 				// Don't leak info about resources under the shroud
-				if (!self.World.LocalShroud.IsExplored(location)) return false;
+				if (!self.Owner.Shroud.IsExplored(location)) return false;
 
 				var res = self.World.WorldActor.Trait<ResourceLayer>().GetResource(location);
 				var info = self.Info.Traits.Get<HarvesterInfo>();