Implement command-based CLI, and start cluster-bringup

This change adds a CLI styled after the Go tool chain, with a design
inspired by that system. It adds 4 new commands, 'run',
'create-cluster', 'join-cluster', and 'version'. Full help is also
supplied.

Local-mode 'run' is fully functional, and 'create-cluster' also works.
I tend to agree with you, and considered it. There are very few "shared" flags, so just adding them to each command might be best. Let me try that.