issue685275 - show retired/unretired items in roundup-admin add pragma display_header to print headers for display command. Header displays designator and retired/active status. Add doc of pragma to affected commands. Add test for code paths.

try:
    # Python 3+.
    from xmlrpc import client, server
    server.SimpleXMLRPCDispatcher
except (ImportError, AttributeError):
    # Python 2.
    import xmlrpclib as client  # noqa: F401
    import SimpleXMLRPCServer as server