Log each change of the WhatsApp connection

The WhatsApp log gets one line for each change of the connection of the
linked device: connected, a failed first connection, a lost connection,
connected again with the length of the outage, a connection that does
not come back by itself, a link, an unlink, and a logout from the phone.
The retries of the library between them log nothing, and the logger of
the library stays off.

Each line says first what happens to the WhatsApp messages, and then the
cause. An unlink clears the time of the last disconnection, so the first
connection of a new link does not count as the end of an outage.

Issue: e4acfcb