Implement the cert-find command for the dogtag CA backend.
    
    Use a new RESTful API provided by dogtag 10+. Construct an XML document
    representing the search request. The output is limited to whatever dogtag
    sends us, there is no way to request additional attributes other than
    to read each certificate individually.
    
    dogtag uses a boolean for each search term to indicate that it is used.
    Presense of the search item is not enough, both need to be set.
    
    The search operation is unauthenticated
    
    Design page: http://freeipa.org/page/V3/Cert_find
    
    https://fedorahosted.org/freeipa/ticket/2528