[improvement] sort json payload in logging

[sjorge]

Zigbee2MQTT:info  2020-08-12 21:40:36: MQTT publish: topic 'zigbee2mqtt/office/lights/panel1', payload '{"state":"OFF","linkquality":31,"update_available":false,"brightness":254,"color_temp":370}'
Zigbee2MQTT:info  2020-08-12 21:40:36: MQTT publish: topic 'zigbee2mqtt/office/lights/panel3', payload '{"update_available":false,"state":"OFF","linkquality":34,"brightness":254,"color_temp":370}'
Zigbee2MQTT:info  2020-08-12 21:40:36: MQTT publish: topic 'zigbee2mqtt/office/lights/panel2', payload '{"state":"OFF","brightness":254,"update_available":false,"linkquality":34,"color_temp":370}'
Zigbee2MQTT:info  2020-08-12 21:40:36: MQTT publish: topic 'zigbee2mqtt/office/lights/panel4', payload '{"state":"OFF","brightness":254,"linkquality":31,"update_available":false,"color_temp":370}'```

The order of panel3 is different, not a huge deal but it makes comparing devices a pain. Would be nice if they were sorted so the order is the same.

[Koenkk]

Implemented!

Changes will be available in the latest dev branch in a few hours (https://www.zigbee2mqtt.io/how_tos/how-to-switch-to-dev-branch.html)