Tying directories directly to an environment or service

Today, with `torus link` you can tie a directory and it's children to a specific organization and project. However, you cannot a directory directly to a service or environment.

In some cases (such as with terraform controlled infrastructure), it'd be nice to be able to tie a directory directly to a specific environment and/or service.

Off the top of my head I can think of a few different ways we could approach this problem:

- Enabling recursive `.torusrc` files, where we'd look up/find the `.torusrc` closest and then layer the settings from subsequent `.torusrc` files in subsequent directories until we reach `$HOME/.torusrc`.
- Enabling a user to specify a service or environment via `.torus.json` either as an option to `torus link` or as a secondary field.

Start at the `torus link` entry point and inspect how `.torusrc` and `.torus.json` currently associate directories with organizations and projects. Compare the proposed recursive `.torusrc` and secondary `.torus.json` approaches, then define completion as allowing a directory to target a specific service or environment.

Written by the indexing model from the issue text.