More shroud refactoring.

This introduces a hash on Shroud which ShroudRenderer
can observe, removing the need to explicitly twiddle
a dirty flag between objects.

Shroud disabling is now done via RenderPlayer, so
enabling the cheat or winning/losing will now give
vis equivalent to an observer.

OpenRA.Game/Traits/Player/DeveloperMode.cs

@@ -81,7 +81,7 @@ namespace OpenRA.Traits
 				case "DevShroudDisable":
 					{
 						DisableShroud ^= true;
-						self.Owner.Shroud.Disabled = DisableShroud;
+						self.World.RenderPlayer = DisableShroud ? null : self.Owner;
 						break;
 					}
 				case "DevPathDebug":