Units that have turrets while deployed now move their turrets back to their initial positions before undeploying

- Tested in TS with all deployable units and did a quick check for obvious issues in TD and RA.

OpenRA.Mods.Common/Activities/WaitForTurretAlignment.cs

@@ -0,0 +1,42 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2018 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, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.Linq;
+using OpenRA.Activities;
+using OpenRA.Mods.Common.Traits;
+
+namespace OpenRA.Mods.Common.Activities
+{
+    public class WaitForTurretAlignment : Activity
+    {
+        readonly Turreted turreted;
+        readonly int desiredAlignment;
+
+        public WaitForTurretAlignment(Actor self, int desiredAlignment)
+        {
+            this.turreted = self.Trait<Turreted>();
+            this.desiredAlignment = desiredAlignment;
+        }
+
+        protected override void OnFirstRun(Actor self)
+        {
+            turreted.StopAiming(self);
+        }
+
+        public override Activity Tick(Actor self)
+        {
+            turreted.DesiredFacing = desiredAlignment;
+            if (turreted.HasAchievedDesiredFacing)
+                return NextActivity;
+            return this;
+        }
+    }
+}