help: Do not create instances to get information about commands and topics
    
    Creating instance requires that complete schema for the command is
    read from schema cache and passed to constructor. This operation takes
    a lot of time. Utilizing class properties and pregenerated help bits
    allows to get the necessary information directly from classes reducing
    time it takes significantly.
    
    https://fedorahosted.org/freeipa/ticket/6048
    
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>