Changes since V0.18c:
-- show default for mqtt.clientid in addon config dialog
Changes since V0.18b:
-- added mqtt.clientid to addon config dialog
Changes since V0.18a:
-- added mqtt.username/password to addon config dialog
Changes since V0.18:
-- update addon VERSION
Changes since V0.16:
-- support MQTT authentication
-- fix topics pushed in response to /get/ request