Access to change $disableListing in Baikal before running the server.

[faridanoosheh]

Using the Baikal image to run a Caldav Server is really helpful. However, any caldav user will have access to the list of all other users by visiting .../dav.php/ url. As mentioned elsewhere it can be deactivated using disableListing. But for an enduser it would be costly to maintain a project for such a minor change.
I would like to suggest to verify the possibility of getting access to this variable so that it can be modified among the other system variables before running the server like what we have here in dav.php.

disableListing is only used once
Thanks