----------------
- Split header into Header, Invalidate and Naming classes.
- Renamed reader to converter, in docs and variables.
- Allow passing directly a converter_id as string.
- Allow converters with one (source_object)
or two parameters (source_object, cache_path_stem).
- Added NameByHashIter.
- Added type checking on source_object using __post_init__.
- Added docstrings.
- Added checks to fail fast when creating Header classes.