webui: entity facets in facet registry
    
    All entity facets are automatically registered as a new type in
    reg.facet.
    
    The type name is: <entity_name>_<facet_name>
    
    The name of facets is kept same, mainly to support the same url routes.
    
    This change allows to get facet instance by calling, e.g.:
      reg.facet.get('user_details')
    
    It allows to make declarative links to facet which are not yet instantiated.
    
    Reviewed-By: David Kupka <dkupka@redhat.com>
    Reviewed-By: Thierry Bordaz <tbordaz@redhat.com>