Make the "debug http" command available for robust as well as the simulator. This allows one to see incoming requests as they happen.

This required making everything use the common MainServer class for registering and retrieving http servers, rather than duplicate structures.

OpenSim/Framework/Servers/HttpServer/BaseHttpServer.cs

@@ -1557,6 +1557,9 @@ namespace OpenSim.Framework.Servers.HttpServer
 
         private void StartHTTP()
         {
+            m_log.InfoFormat(
+                "[BASE HTTP SERVER]: Starting {0} server on port {1}", UseSSL ? "HTTPS" : "HTTP", Port);
+
             try
             {
                 //m_httpListener = new HttpListener();