Include whether the PR passed the threshold or not in the API data
    
    Basically, if the project requires a minimal score to merge PR,
    the data returned by the API will be either a ``True`` or
    ``False``.
    If the project does not enforce any score to merge the PR, the
    data returned by the API will be ``None``.
    
    Fixes https://pagure.io/pagure/issue/4014
    
    Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>