Implementation of the automated D2k Carryall

Closes #2246

OpenRA.Mods.RA/Activities/Air/HeliFlyCircle.cs

@@ -0,0 +1,45 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2014 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation. For more information,
+ * see COPYING.
+ */
+#endregion
+
+using System;
+using System.Collections.Generic;
+using OpenRA.Traits;
+using OpenRA.Mods.RA.Activities;
+using OpenRA.Mods.RA.Traits;
+
+namespace OpenRA.Mods.RA.Activities
+{
+	public class HeliFlyCircle : Activity
+	{
+		readonly Helicopter helicopter;
+
+		public HeliFlyCircle(Actor self)
+		{
+			helicopter = self.Trait<Helicopter>();
+		}
+
+		public override Activity Tick(Actor self)
+		{
+			if (IsCanceled)
+				return NextActivity;
+
+			if (HeliFly.AdjustAltitude(self, helicopter, helicopter.Info.CruiseAltitude))
+				return this;
+
+			var move = helicopter.FlyStep(helicopter.Facing);
+			helicopter.SetPosition(self, helicopter.CenterPosition + move);
+
+			var desiredFacing = helicopter.Facing + 64;
+			helicopter.Facing = Util.TickFacing(helicopter.Facing, desiredFacing, helicopter.ROT / 3);
+
+			return this;
+		}
+	}
+}