6f5e80b webui: add parent link to widgets in ContainerMixin

Authored and Committed by pvoborni 9 years ago
    webui: add parent link to widgets in ContainerMixin
    
    Standard facets sets `facet` attribute to widgets. This one adds
    similar, more generic `parent` attribute which should be used for going through
    the hierarchy up to top.
    
    Reviewed-By: Endi Sukma Dewata <edewata@redhat.com>