rtl_433 data integrity check

Porting issue rtl_433-to-mqtt#3 (closed)

rtl_433 attempts to validate messages using any checksums available, but this doesn't always work, and bad data gets through.

Since Acu-rite sensors publish 2 or 3 copies of each update message, they should be used to verify the integrity of the data. E.G. require 2 identical copies of the data before pushing it to MQTT.