Implement replica promotion functionality
    
    This patch implements a new flag --promote for the ipa-replica-install command
    that allows an administrative user to 'promote' an already joined client to
    become a full ipa server.
    
    The only credentials used are that of an administrator. This code relies on
    ipa-custodia being available on the peer master as well as a number of other
    patches to allow a computer account to request certificates for its services.
    
    Therefore this feature is marked to work only with domain level 1 and above
    servers.
    
    Ticket: https://fedorahosted.org/freeipa/ticket/2888
    
    Signed-off-by: Simo Sorce <simo@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>