[entities] Move CWSource update_config method as a function in 3.15 migration script
This script is the only caller of this method. In the code of the function,
drop "skip_unknown" argument and continue accordingly upon OptionError.
Startup views
-------------
Startup views are views requiring no context, from which you usually start
browsing (for instance the index page). The usual selectors are
:class:`~cubicweb.predicates.none_rset` or :class:`~logilab.common.registry.yes`.
You'll find here a description of startup views provided by the framework.
.. automodule:: cubicweb.web.views.startup
Other startup views:
*schema*
A view dedicated to the display of the schema of the instance
.. XXX to be continued