Previously this lived in a separate repo docker-hub-images, shared with
other products. Having multiple products sharing a repo complicates
release processes and works against some assumptions made by the Dockerhub
build system.
The "full" Dockerfile contains a Terraform binary built from source, and
so it can be used with any arbitrary Terraform source tree. This doesn't
yet include the "light" Dockerfile, which instead makes an image from
official binaries already on releases.hashicorp.com. That will follow in
a subsequent commit.
