Added monitoring with nagios

This new version is using an external puppet nagios module.
Which makes more sense since this is not directly related with openstack anyway.
This has the advantage to reduce impact on quickstack as much as possible.

This add a 'Nagios hostgroup' and monitoring::server and monitoring::client to wrap calls to the external nagios module. 

This is impacting only non HA to start with (Neutron/Nova_network controllers/compute/networker)