Adding new fields and home location methid to presence. Adding cleanup

(deleting all but one presence record) on logout so that they don't pile up.

OpenSim/Data/IPresenceData.cs

@@ -51,6 +51,9 @@ namespace OpenSim.Data
         PresenceData Get(UUID sessionID);
         void LogoutRegionAgents(UUID regionID);
         bool ReportAgent(UUID sessionID, UUID regionID, string position, string lookAt);
+        bool SetHomeLocation(string userID, UUID regionID, Vector3 position, Vector3 lookAt);
         PresenceData[] Get(string field, string data);
+        void Prune(string userID);
+        bool Delete(string field, string val);
     }
 }