[skeleton] Add "cubicweb.session.secret" to development.ini Commented as other "secret" settings. At least, now all settings are present in the development.ini file. [ci skip]

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