Provide sufficient context to check 'delete' permission in AjaxEditRelationCtxComponent Call rdef.check only when both fromeid and toeid are available. Though only call it once (for the first encountered related entity). Factorize a bit to keep handling of CSS/JS addition the same. Closes #3670209.

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