[refactoring] introduce add_etype_button function to properly create button to add a new entity also properly use cw_create_url to generate the URL to add the entity

#! /bin/sh -e

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