Reorganize PlayerReference loading to enable upgrade rules for them.

The PlayerReference definitions are now stored
as raw MiniYamlNodes in the map.

OpenRA.Game/Map/MapPlayers.cs

@@ -0,0 +1,75 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2015 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.Collections.Generic;
+using System.Linq;
+using OpenRA.Traits;
+
+namespace OpenRA
+{
+	public class MapPlayers
+	{
+		public readonly Dictionary<string, PlayerReference> Players;
+
+		public MapPlayers() : this(new List<MiniYamlNode>()) { }
+
+		public MapPlayers(IEnumerable<MiniYamlNode> playerDefinitions)
+		{
+			Players = playerDefinitions.Select(pr => new PlayerReference(new MiniYaml(pr.Key, pr.Value.Nodes)))
+				.ToDictionary(player => player.Name);
+		}
+
+		public MapPlayers(Ruleset rules, int playerCount)
+		{
+			var firstRace = rules.Actors["world"].Traits
+				.WithInterface<CountryInfo>().First(c => c.Selectable).Race;
+
+			Players = new Dictionary<string, PlayerReference>
+			{
+				{
+					"Neutral", new PlayerReference
+					{
+						Name = "Neutral",
+						Race = firstRace,
+						OwnsWorld = true,
+						NonCombatant = true
+					}
+				},
+				{
+					"Creeps", new PlayerReference
+					{
+						Name = "Creeps",
+						Race = firstRace,
+						NonCombatant = true,
+						Enemies = Exts.MakeArray(playerCount, i => "Multi{0}".F(i))
+					}
+				}
+			};
+
+			for (var index = 0; index < playerCount; index++)
+			{
+				var p = new PlayerReference
+				{
+					Name = "Multi{0}".F(index),
+					Race = "Random",
+					Playable = true,
+					Enemies = new[] { "Creeps" }
+				};
+				Players.Add(p.Name, p);
+			}
+		}
+
+		public List<MiniYamlNode> ToMiniYaml()
+		{
+			return Players.Select(p => new MiniYamlNode("PlayerReference@{0}".F(p.Key),
+				FieldSaver.SaveDifferences(p.Value, new PlayerReference()))).ToList();
+		}
+	}
+}