Configuration CSS tweak for the dev website.

The goal of this is to prevent users from mistakenly using the development
website as if it were the real one.
Added dev website nginx configuration.
Restored the maintenance page + nginx config.

The maintenance mode is triggered with a file.
$ touch /var/www-prod/maintenance.mode # start maintenance
$ rm /var/www-prod/maintenance.mode    # end maintenance
Fixed parenthesis and repository update behavior.

Don’t update repository if we’re not about to commit. This allow to use
the script only to fetch translations.
#501 New page, only English and French for now.
#501 Added 13 translations
#499 Force timestamp on assets.
Merge branch 'dev' into prod