* Makefile: improve 'clean' target to remove _build/ META.json and META.yml
* Makefile: add 'install' target to ease Debian packaging
* Build.PL: define 'module_name' to prevent Debian packaging from issuing a
  warning
Add Nagios plugins configuration: etc/nagios-plugins/config/*.cfg
Add NRPE configuration: etc/nagios/nrpe.d/*.cfg