- every object now has `as_dict/from_dict` methods to help save work as e.g.
json files.
- this introduces a breaking change! The functionality previously accessible
via `DefectSystem.as_dict()` in versions < 2.0.0 is now accessible via
`DefectSystem.concentration_dict()`
- this has also resulted in some changes to the CLI input file format. See
the docs for new formatting requirements.