Add `--syslog` parameter

[bmario]

Depends on #188

• [ ] Parameter --syslog -> enables directly logging to syslog server and optionally argument the targeted syslog server (instead of default syslog socket)
• [ ] Enable as optional feature

[bmario]

There is the syslog2 python package that provides a SyslogLogHandler.

This takes several arguments, which are interesting.

• address should be parsed from the argument provided by the user to --syslog
  • Nothing -> address == "local"
  • A string in the hostname:port format -> address == value.split(":")
  • A string representing a path -> address == value
  • Anything else: error
• facility should probably be set "daemon" or "user"
• program should be the MetricQ token, this might turn out as impossible

[bmario]

There is also the standard lib version here: https://docs.python.org/3/library/logging.handlers.html#logging.handlers.SysLogHandler

That might be more than enough for our use case already.