[pkg] Specify priority “optional” instead of the obsolete “extra” Quoting Lintian, “Since Debian Policy version 4.0.1, the priority extra has been deprecated.” So let's use “optional” instead.

etc/init.d
etc/cubicweb.d
etc/bash_completion.d
usr/bin
usr/share/doc/cubicweb-ctl
var/log/cubicweb
var/lib/cubicweb/backup
var/lib/cubicweb/instances