kill register_appobject_class method, simplifying autoregistration. Update test accordingly (test which manually registers object should also properly call there __register__ method). Drop the disable-appobjects config file entry: no one used it since its introduction years ago.

#! /bin/sh -e
 
case "$1" in
    purge)
        rm -rf /etc/cubicweb.d/
    	rm -rf /var/run/cubicweb/
	rm -rf /var/log/cubicweb/
	rm -rf /var/lib/cubicweb/
    ;;
esac
 
#DEBHELPER#
 
exit 0