Add Sensor reading classes.
Improve documentation and add to_dict method.
Add sensor readings to module init
Change import type; basic impl of rx_io_data
Log all packets
Various bug fixes
Improve logging info for startup and shutdown

Add coordinator halting to logging and add formatting columns.
Add environmental and plug level sensor checks
Ignore packets from unidentified nodes
Add more debugging for serialport
Add voltage / current normalization
Fix mongo; calibrate killawatt
Merge branch 'master' into update-db-cols