Add ScriptTags trait

This allows actors to be tagged with arbitrary strings.
Also includes ScriptTagsInit and MapGlobal.ActorsWithTag
  which expose this functionality to map scripters.

OpenRA.Mods.Common/Traits/ScriptTags.cs

@@ -0,0 +1,58 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2016 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.Collections.Generic;
+using OpenRA.Traits;
+
+namespace OpenRA.Mods.Common.Traits
+{
+	[Desc("Allows this actor to be 'tagged' with arbitrary strings. Tags must be unique or they will be rejected.")]
+	public class ScriptTagsInfo : UsesInit<ScriptTagsInit>
+	{
+		object ITraitInfo.Create(ActorInitializer init) { return new ScriptTags(init, this); }
+	}
+
+	public class ScriptTags
+	{
+		readonly HashSet<string> tags = new HashSet<string>();
+
+		public ScriptTags(ActorInitializer init, ScriptTagsInfo info)
+		{
+			if (init.Contains<ScriptTagsInit>())
+				foreach (var tag in init.Get<ScriptTagsInit, string[]>())
+					tags.Add(tag);
+		}
+
+		public bool AddTag(string tag)
+		{
+			return tags.Add(tag);
+		}
+
+		public bool RemoveTag(string tag)
+		{
+			return tags.Remove(tag);
+		}
+
+		public bool HasTag(string tag)
+		{
+			return tags.Contains(tag);
+		}
+	}
+
+	/// <summary>Allows mappers to 'tag' actors with arbitrary strings that may have meaning in their scripts.</summary>
+	public class ScriptTagsInit : IActorInit<string[]>
+	{
+		[FieldFromYamlKey] readonly string[] value = new string[0];
+		public ScriptTagsInit() { }
+		public ScriptTagsInit(string[] init) { value = init; }
+		public string[] Value(World world) { return value; }
+	}
+}