Antag Datums. Oh also minds. (#100)

AKA: Minds and there's a stupid basic roles framework.

Content.Server/Players/PlayerData.cs

@@ -0,0 +1,47 @@
+using Content.Server.Mobs;
+using SS14.Server.Interfaces.Player;
+using SS14.Shared.Network;
+
+namespace Content.Server.Players
+{
+    /// <summary>
+    ///     Content side for all data that tracks a player session.
+    ///     Use <see cref="PlayerDataExt.ContentData(IPlayerData)"/> to retrieve this from an <see cref="IPlayerData"/>.
+    /// </summary>
+    public sealed class PlayerData
+    {
+        /// <summary>
+        ///     The session ID of the player owning this data.
+        /// </summary>
+        public NetSessionId SessionId { get; }
+
+        /// <summary>
+        ///     The currently occupied mind of the player owning this data.
+        /// </summary>
+        public Mind Mind { get; set; }
+
+        public PlayerData(NetSessionId sessionId)
+        {
+            SessionId = sessionId;
+        }
+    }
+
+    public static class PlayerDataExt
+    {
+        /// <summary>
+        ///     Gets the correctly cast instance of content player data from an engine player data storage.
+        /// </summary>
+        public static PlayerData ContentData(this IPlayerData data)
+        {
+            return (PlayerData)data.ContentDataUncast;
+        }
+
+        /// <summary>
+        ///     Gets the correctly cast instance of content player data from an engine player data storage.
+        /// </summary>
+        public static PlayerData ContentData(this IPlayerSession session)
+        {
+            return session.Data.ContentData();
+        }
+    }
+}