cannot configure facelet refresh period in common template

In debug mode, we need to configure facelets for reloading templates when they are modified. In the past, we were just editing by hand the nuxeo.properties file. This is not allowed anymore as that file is now generated by the templating system.
We want instead to edit a variabe in the nuxeo.conf file for injecting the value in the template.
The property and it's default value is to be defined by the 'common' template.