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.