Add request received/handling stats for caps which are served by http poll handlers.

This adds explicit cap poll handler supporting to the Caps classes rather than relying on callers to do the complicated coding.
Other refactoring was required to get logic into the right places to support this.

OpenSim/Framework/Servers/HttpServer/PollServiceEventArgs.cs

@@ -55,12 +55,26 @@ namespace OpenSim.Framework.Servers.HttpServer
             Inventory = 2
         }
 
+        public string Url { get; set; }
+
+        /// <summary>
+        /// Number of requests received for this poll service.
+        /// </summary>
+        public int RequestsReceived { get; set; }
+
+        /// <summary>
+        /// Number of requests handled by this poll service.
+        /// </summary>
+        public int RequestsHandled { get; set; }
+
         public PollServiceEventArgs(
             RequestMethod pRequest,
+            string pUrl,
             HasEventsMethod pHasEvents, GetEventsMethod pGetEvents, NoEventsMethod pNoEvents,
             UUID pId, int pTimeOutms)
         {
             Request = pRequest;
+            Url = pUrl;
             HasEvents = pHasEvents;
             GetEvents = pGetEvents;
             NoEvents = pNoEvents;