Bad interface of run-terraform

[yannham]

The default flake template creates a dev shell which wraps terraform with a custom script (cf #37). The CLI UX of this script is a bit limited: it doesn't allow to pass through commands or arguments to the underlying terraform invocation without first specifying a Nickel file (e.g. using -- init --foo --bar), doesn't support --help or --version and the default usage message is missing a basic description of the command.