idviews: Support specifying object names instead of raw anchors only
    
    Improve usability of the ID overrides by allowing user to specify the common name of
    the object he wishes to override. This is subsequently converted to the ipaOverrideAnchor,
    which serves as a stable reference for the object.
    
    Part of: https://fedorahosted.org/freeipa/ticket/3979
    
    Reviewed-By: Petr Viktorin <pviktori@redhat.com>
    Reviewed-By: Petr Vobornik <pvoborni@redhat.com>
    Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>