Invert the name of namespace commands to match the snapshots and replication form

In our shell, we are inconsistent in the way that we color/group commands. The majority though seem to be <COMMAND> '-' <GROUP> as in list_snapshots and list_peers for snapshotting and replication respectively wherease namespaces does 'namespaces_list'.

If we could start over, I'd have gone w/ the namespaces format but we are where we are..... lets fix this before we release post ns commit.