[server] refactor cleanup() code used by "cubicweb-ctl delete"
Try to make each logical step (i.e. "delete database" and "delete user")
a bit more visible and explicit.
This is a preparatory work to easily plug the "delete namespace" feature.
../../doc/book usr/share/doc/cubicweb-documentation
../../doc/html usr/share/doc/cubicweb-documentation
../../debian/cubicweb-doc usr/share/doc-base/cubicweb-doc