Add some more validation of parameters to the icinga2::server's parameters.
Make the default value of the server_install_nagios_plugins value a boolean version true instead of a string version 'true'.
Added validation to nrpe.pp's parameters.
Added validation to the icinga2::nrpe::command class' parameters.
Added validation to the icinga2::nrpe::plugin class' parameters.
Added validation to the icinga2::object::apply_service_to_host class' parameters.
Added validation to the icinga2::object::host class' parameters.
Added validation to the icinga2::object::hostgroup class' parameters.
Added validation to the icinga2::object::idomysqlconnection class' parameters.
Added validation to the icinga2::object::idopgsqlconnection class' parameters.
Added validation to the icinga2::object::service class' parameters.
Added validation to the icinga2::object::user class' parameters.
Added validation to the icinga2::object::usergroup class' parameters.
Remove Debian from the regex since it's not a supported distro yet.
For Ubuntu systems, switch to adding the Icinga PPA instead of the release snapshot apt repo.
Changed the DB schema file paths for RHEL/CentOS.
Bump the version of the apt module that's required by metadata.json.
Added a servicegroup object defined type.
Added an ERB template to create servicegroup object files.
Added a section to the README for servicegroup objects with a usage example.