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

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