adds the ability to clear db

kordophoned/src/dbus/server_impl.rs

@@ -99,6 +99,10 @@ impl DbusRepository for ServerImpl {
                 }).collect()
             })
     }
+
+    fn delete_all_conversations(&mut self) -> Result<(), dbus::MethodErr> {
+        self.send_event_sync(Event::DeleteAllConversations)
+    }
 } 
 
 impl DbusSettings for ServerImpl {