ipaclient: implement thin client
    
    Dynamically create plugin package for the remote server with modules and
    commands based on the API schema when client API is finalizes. For in-tree
    API instances, use ipalib.plugins directly.
    
    https://fedorahosted.org/freeipa/ticket/4739
    
    Reviewed-By: David Kupka <dkupka@redhat.com>