Add log when heartbeating

plugin.py

@@ -111,6 +111,7 @@ class BasePlugin(object):
     def on_heartbeat(self):
         """Time to heartbeat :)"""
         if self._pooling_current_step >= self._pooling_steps:
+            Domoticz.Log(f"onHeartbeat {self._pooling_steps*self._heartbeat//60} min")
             query = {
                 'lat': Parameters["Mode1"],
                 'long': Parameters["Mode2"],