I want receiver to know when message was originally created. This adds
timestamp to messages and passes it via send proc. Client needs to
send it where possible. So far, MQTT format can't include it without
change, so I'm adding a new proto version. This change can read the
new version. Once that's well-enough distributed I can start sending
using it. Other transmission types than MQTT are for later.
This is meant to replace the relay eventually, but for now it's a new
option, like BT or SMS, to be chosen. Protocol is handled in common/
code for the first time, meaning that linux and android interact without
the need to keep two platforms in sync. Linux uses lib-mosquitto, and
Android uses eclipse's Paho client (the generic java version, not the
one that uses four-year-old Service patterns and so crashes for SDK >=
26.)
