A round of improvements to facilitate use and maintenance (no changes to results):

- small UX improvements on lattice scripts.
- Add an option to pass a list of lexeme ids to use for the next computation (instead of all lexemes).
- More consistent import of paradigms / patterns.
- Modernize the build process: move to pyproject.toml and remove setup.cfg.
- Default to cpus=1 due to incompatibility with Mac & Windows.
- Add option to autosort cells in heatmaps, according to result similarity.
- rewrite docs and change docs theme.