Two options, 'path' to the file and 'mode' of permissions(not umask, recommend 666 as default as
nginx/other reverse proxies write to it and it's setup as user www-data)

For the moment, leave the option to always create a PID lockfile turned on by default

Rename ListenerConfig to TCPListenerConfig, then Union them together into ListenerConfig.
This spidered around a bit, but I think I got it all. Metrics and manhole have been placed
behind a conditional in case of accidental putting them onto a unix socket.

Use new helpers to get if a listener is configured for TLS, and to help create a site tag
for logging.

There are 2 TODO things in parse_listener_def() to finish up at a later point.

… socket.

This prevents an exception when an IP address can not be retrieved for a request.

…ttier.

…t with metrics or manhole.

… permission of 0o666 and add a few comments saying where the default IS declared.

…resource

…per(and add docstring)

…lid, remove a TODO line

… what is being retrieved and why

…g the byte string.

…path nor port is declared(and fix a typo)