follow yams api change: attributes permissions are now defined for an 'update' action, no more 'add' / 'delete' which makes no sense in such case. fix afs.relations_by_section permissions checking of object relation on the way.

debian/tmp/usr/lib/PY_VERSION/site-packages/cubicweb/etwist/ usr/lib/PY_VERSION/site-packages/cubicweb/