[primary] refactor primary view handling of relation's label to properly handle label optionaly specified in dispctrl (no more default set) and use contextual translation by default. Also, consistent handling in attributes, relations and sideboxes section. Introduce new support_args function to use when possible instead of try/except TypeError.

#!/usr/bin/env python
from cubicweb.cwctl import run
import sys
run(sys.argv[1:])