Changes
- Template is now subscriptable (allows set, delete, get by index)
- Default rule aggregation exposed via `Settings`
- `duplicate_groundings` are now present in `Metadata.__str__`
- Global setter for the graphviz path
- Split dataset building into two steps - groundings can now be rendered
- Alternative way to define rule bodies using `&` (e.g, `R.a <= R.b & R.c`)
- Calling `.draw()` now display the image (if `show=True` and no path has been provided)