Message abstraction

BaseMessage.cs

	public abstract class BaseMessage
	{
		protected string Source;
		protected string Destination;
		protected string Content;

		protected BaseMessage(string source, string destination, string content)
		{
			Source = source;
			Destination = destination;
			Content = content;
		}
	}

PrivateMessage.cs

	public class PrivateMessage : BaseMessage
	{
		public string Sender { get { return source; } }
		public string Receiver { get { return destination; } }
		public string Message { get { return content; } }

		public PrivateMessage(string sender, string receiver, string message)
			: base(sender, receiver, message)
		{
		}
	}