Improve MQTT topic usage for feedback messages. (#663)
Improve MQTT topic usage for feedback messages. (#663)

- Move log messages to their own MQTT topic. (ir_server/log)
- Set up a Last Will & Testament topic (ir_server/status)
- Change MQTT QoS to 1, which should hopefully handle messages lost during disconnects.

Tested log and LWT functionality on my personal device. Everything seems to work as normal.

Fixes #662
Ref #661


markszabo/IRremoteESP8266,markszabo/IRremoteESP8266,markszabo/IRremoteESP8266,markszabo/IRremoteESP8266