[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.

fontcolor = 'black'
bgcolor = '#FFFFFF'
stylesheets = sheet['stylesheets'] + ['%s/mycube.css' % datadir_url]