On a single-group cluster, we proceed as before. On multi-group
clusters, we require selection of the desired group (currently via UUID
only).

Signed-off-by: Iustin Pop <iustin@google.com>
Reviewed-by: Balazs Lecz <leczb@google.com>

This simplifies the maintenance of the man pages, and unifies the rst-to-*
converter to pandoc.