Comment 4 for bug 1183109

It's missing from the "basic commands" list, but is listed in `juju help commands` (referenced in the default help) and described in `juju help destroy-environment`.

What's the rationale for adding destroy-environment specifically to the most-important-commands list? If we add everything, it becomes a somewhat unhelpful firehose -- not quite as bad as bzr would be, but still not very pleasant -- and it seems to us that the bzr model is actually helpful and worth following.