Use rich logging for Pelican server

This way we can see the server requests.

Remove shebang lines from generated pelicanconf.py and publishconf.py

Adjust suffix in server to allow redirection when needed

These configuration files do not need a #! line as they are not intended to be
executed directly and are not marked as executable. (In practise this doesn't
cause any problems - it just came up in a Guix bug report because Guix
transforms the #! lines.)

The "coding: utf-8" lines are also no longer required now that Pelican is Python
3 only.

Folders without index.html has to be redirected (/foo -> /foo/) for
directory listing to work properly. Skip '/' suffix if original path
does not have it so that base class can return a redirect.