Add 'server' stats information to pCampbot, as used elsewhere in OpenSimulator

This adds the "show stats", "stats record", etc. commands and information on available Threadpool threads, etc.
It also adds the Watchdog which logs warnings if time between executions is unexpectedly large.

OpenSim/Framework/Monitoring/ServerStatsCollector.cs

@@ -82,6 +82,9 @@ namespace OpenSim.Framework.Monitoring
         // IRegionModuleBase.Initialize
         public void Initialise(IConfigSource source)
         {
+            if (source == null)
+                return;
+
             IConfig cfg = source.Configs["Monitoring"];
 
             if (cfg != null)