The `.env` file shouldn't live in the `/config` directory when it is created, but
currently, the `.env_sample` file lives within `/config`. This can be confusing and
cause ENV var issues if someone duplicates `.env_sample` and renames it to `.env`,
because none of their ENV variables will get picked up, since their `.env` file will
mistakenly end up in `/config`.
This change moves `.env_sample` out of `/config`, and updates the documentation/relevant
.yml files accordingly.
