Added LineBuildNode trait to filter which structure(s) a LineBuild actor can be attached to.

OpenRA.Mods.RA/Buildings/LineBuildNode.cs

@@ -0,0 +1,24 @@
+#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 OpenRA.FileFormats;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.RA.Buildings
+{
+	[Desc("LineBuild actors attach to LineBuildNodes.")]
+	public class LineBuildNodeInfo : TraitInfo<LineBuildNode>
+	{
+		[Desc("This actor is of LineBuild 'NodeType'...")]
+		public readonly string[] Types = { "wall" };
+	}
+
+	public class LineBuildNode {}
+}