Re-organize in-memory character profile storage.

Now uses a dictionary of int -> profile instead of an array filled with nulls.

Content.Shared/Network/NetMessages/MsgSelectCharacter.cs

@@ -0,0 +1,33 @@
+using Lidgren.Network;
+using Robust.Shared.Interfaces.Network;
+using Robust.Shared.Network;
+
+namespace Content.Shared.Network.NetMessages
+{
+    /// <summary>
+    /// The client sends this to select a character slot.
+    /// </summary>
+    public class MsgSelectCharacter : NetMessage
+    {
+        #region REQUIRED
+
+        public const MsgGroups GROUP = MsgGroups.Command;
+        public const string NAME = nameof(MsgSelectCharacter);
+
+        public MsgSelectCharacter(INetChannel channel) : base(NAME, GROUP) { }
+
+        #endregion
+
+        public int SelectedCharacterIndex;
+
+        public override void ReadFromBuffer(NetIncomingMessage buffer)
+        {
+            SelectedCharacterIndex = buffer.ReadVariableInt32();
+        }
+
+        public override void WriteToBuffer(NetOutgoingMessage buffer)
+        {
+            buffer.WriteVariableInt32(SelectedCharacterIndex);
+        }
+    }
+}