Paroxython

Launching Paroxython on itself raised some corner-case errors. Fixed or improved:

- Don't calculate the index shape for non-nested indexes. Improve performance for index-heavy programs like `compare_spans.py`.
- Make dumped filenames clickable under VS code (more convenient).
- Don't version the results of paroxython applied to itself.
- Fix a misclassification of `from . import foobar`.
- Use a numeric suffix for feature `variety` instead of a sequence of stars.
- Ensure all one-liners have a `whole_span` feature. This includes programs whose flat ast contains only one `"/_pos="`, for instance:
python
from . import foobar

- Prevent a potential parsing error on certain strings. These strings are those used in the flat AST, such as `"/_pos="`. Some regexes mistook them for the real thing.

Main changes
- Support non-flat directory structure, as long as the import syntax is:
python
from a.b.c import d

- New [documentation section](https://laowantong.github.io/paroxython/user_manual/index.html#importations).
- `import` is now a root in the default taxonomy.
- Internals: rename user type `ProgramName` (and derivative's) into `ProgramPath`.
- The key `name` for the `--format` option of `paroxython recommend` is now `path`.
- A new key `name` is added.

In other news
- The success, warning and error messages are now colorised (on certain terminals).
- New CLI error messages when referring to a non-existent file or directory.

If you have built a tag database with the command:


paroxython collect DIRECTORY


... you can now get the recommendations with:


paroxython recommend DIRECTORY


Previously, it was necessary to provide the tag database explicitly, i.e.:


paroxython recommend DIRECTORY_db.json

Suppress `sys.path` injection during preprocessing cleanup.