Add VTOL landing exhaust animation.

OpenRA.Mods.Common/TraitsInterfaces.cs

@@ -147,6 +147,11 @@ namespace OpenRA.Mods.Common.Traits
 		void StoppingResupply(Actor self, Actor host);
 	}
 
+	[RequireExplicitImplementation]
+	public interface INotifyTakeOff { void TakeOff(Actor self); }
+	[RequireExplicitImplementation]
+	public interface INotifyLanding { void Landing(Actor self); }
+
 	[RequireExplicitImplementation]
 	public interface INotifyPowerLevelChanged { void PowerLevelChanged(Actor self); }
 	public interface INotifySupportPower { void Charged(Actor self); void Activated(Actor self); }