Changed some parameters to work with debian-like distros

[tiengo]

Added some parameters to work with debian-like distros. Package name, service name, config dirs. "www-data" user were added to nagios group to execute external command via web interface.

[alvagante]

good patch, thank you, I have some concerns on the www-data user.... if it's already defined elsewhere we have a duplicate resource error... we should find a less radical way to manage its groups... and since this is a nagios module I'd do it managing directly nagios related resources