Global local.env files

[andyneff]

Current every project has an local.env file. But a user cannot have a personal local.env equivalent file that can affect all projects, nor can a computer have a local.env equivalent that would affect every project on there.

Suggested order and names:

1. /etc/just_local.env or /usr/local/share/just/local.env not sure which is better. The first seems more right
2. ~/.just_local.env or ~/.config/just/local.env or ~/.local/share/just/local.env not sure which is better. The first two seem more right
3. {project}/local.env
4. {project}/{project}.env
5. /etc/just_local_post.env or /usr/local/share/just/local_post.env not sure which is better
6. ~/.just_local_post.env or ~/.config/just/local_post.env or ~/.local/share/just/local_post.env not sure which is better
7. {project}/local_post.env

The order is intentional, so the user can override the system, and the project can override the user/system, and always gets the last call