Added Gates

FIXUP: account for full gate footprint when updating neighbours.

FIXUP: gate-wall connection adjacency yaml.

OpenRA.Game/Traits/TraitsInterfaces.cs

@@ -284,6 +284,13 @@ namespace OpenRA.Traits
 		bool CanEnterTargetNow(Actor self, Target target);
 	}
 
+	[RequireExplicitImplementation]
+	public interface ITemporaryBlocker
+	{
+		bool CanRemoveBlockage(Actor self, Actor blocking);
+		bool IsBlocking(Actor self, CPos cell);
+	}
+
 	public interface INotifyBlockingMove { void OnNotifyBlockingMove(Actor self, Actor blocking); }
 
 	public interface IFacing