Initial outer testing of 4 discovery modes done ok

Design for discovery agents done

Default incoming message callback added to router, for logging/debug

Router unknown message handling callback registration is cleaner

Neater callback mechanism for device class instances to use. ...

This new architecture ensures default message processing always happens

Fixed bug where sensorid was always zero in csv log

Synthetic receive working in monitor_mihome.py

switch.py renamed as control_mihome.py, rewritten for new OO interface