Terraform is way bigger than the core CLI tools and the language
now, and the docs have grown accordingly. So we're adding a
global index page to help users get around the many sections of the
docs site, and bumping the CLI/core docs down so they're no longer at the
top of the hierarchy.
The "right" (as in, conceptually pure) way to do this would be to actually
create a new level of directory hierarchy in between. But that would be real
expensive and annoying — the amount of 301s and links to edit would be
monumental, and it wouldn't gain us much beyond a certain picture-straightening
satisfaction, so I'm resisting the temptation.
