BZ #1122663 - Add Generic RHEL 7 and Ceph OSD node types

https://bugzilla.redhat.com/show_bug.cgi?id=1122663

This patch creates two new roles. A Generic RHEL 7 role and a Ceph OSD
node role. The Ceph OSD role does not have any additional configuration,
as the installation of Ceph will be handled externally.