Formalize process for `diode` settings files

### System Configuration

> Changed the format of diode backup and restore files to [JSON](https://github.com/acep-uaf/data-diode/blob/c10a4ba3a5de3a5c5a1b12b5b13f7ec6d7ccd043/config/B4-0144-355112.json) for easier human readability.

- `config/settings.yaml`
  - #37 
  - #30