NagiosOutput improvements: send_nsca support, explicit host/service, skip certificate verification

- Added support for sending nagios passive checks using send_nsca; config options: send_nsca_bin, send_nsca_args, send_nsca_timeout
- Added configuration parameters to Nagios output for finer control of the nagios data: nagios_host, nagios_service_description
- Added a configuration parmeter to skip certificate checks when using https: insecure_tls_skip_verify