debian packaging

Package the application under a debian package, to be shipped via our APT repository. The whole application is placed under /opt/gnugen-member-management since splitting it 'properly' would be painful (and useless...).

Left to do:

• Define a license (see #12 (closed)).
• Find a way to ignore the lintian errors.
• Place configuration under /etc.
• Ship a systemd unit.
• Manage local user used to run the application.