[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.

bgcolor = '#000000'
stylesheets = ['%s/cubicweb.css' % datadir_url]
logo = '%s/logo.png' % datadir_url
lazy = lazystr('%(bgcolor)s')