Add support for rfc3339 postfix log lines on sockets and stdin
Support receiving log lines with the "modern" [1] rsyslog format, via stdin or socket:
2021-05-16T00:01:44.278515+02:00 mail postfix/postscreen[17274]: Useless Payload
enable it with -log_format rfc3339
or LIGHTMETER_LOG_FORMAT=rfc3339
[1] more info at https://rsyslog-5-8-6-doc.neocities.org/rsyslog_conf_templates.html
Edited by Leandro Santiago