[selectors] match_kwargs and match_form_params selectors both accept a new `once_is_enough` argument (closes #1990438) also fix docstring of match_exception and references to selectors in the book.

#! /bin/sh -e

if [ -x "/etc/init.d/cubicweb-ctl" ]; then
    invoke-rc.d cubicweb-ctl restart || true
fi
 
 
#DEBHELPER#
 
exit 0