Add a README to certificate profile templates directory
    
    There have been several instances of people using the profile
    configuration template files as actual profile configurations,
    resulting in failures and support load.  Add a README to the profile
    template directory to explain that these files should not be used
    and advise of the recommend procedure.
    
    Fixes: https://pagure.io/freeipa/issue/7014
    Reviewed-By: Martin Basti <mbasti@redhat.com>