Monitor NGINX
    
    Equip all NGINX servers with a stats listener and exporter and
    configure the collection through Prometheus.
    Since we do not have a dedicated role for NGINX, use a new
    mine function collecting state includes, and apply the NGINX
    monitoring to all including nginx.config.
    
    Signed-off-by: Georg Pfuetzenreuter <mail@georg-pfuetzenreuter.net>