Installs the icinga client (Nagios plugins and NRPE) on client nodes.

Installs the icinga server software (Icinga, Icinga2) on master nodes.

Class icinga::server is intended to be installed a single server.  If you want to include
apt and apache elsewhere in the manifest, you will need to comment them out of server.pp
to avoid duplicate resource definitions.  It also assumes you will NOT run mysql/postgres
on the master.  You can if you want, but this module doesn't include that.