add new Log AREAs for MQTT & KNX

[mivola]

• currently there are these AREAs defined: (main|network|bus|update|other|all)
• see https://github.com/john30/ebusd/wiki/2.-Run#log-options
• it would be very helpful to have also "knx" and "mqtt" in this list, b/c currently you need to set other:debug to see knx debug messages but then you also get sooo many mqtt messages...