Add munin-node monitoring setting.

This commit fixes #160.
Merge branch 'id/160' into dev
Include /etc/nagios/servicegroups to the Nagios configuration storage directory.

This commit refs #92.
Add munin-node servicegroups.

This commit refs #92.
Add localhost's munin-node service to the munin servicegroup.

This commit refs #92.
Add sakura-vps#001's munin-node service to the munin servicegroup.

This commit fixes #92.
Merge branch 'id/92' into dev
Merge branch 'dev'