Python-sa-gwdata

- Implement attribute access on ``Wells`` objects.

- Add ``ObsNo.parse()`` class method which ignores exceptions.

- Tweak release documentation and links

- Add ``Well`` class for ID parsing
- Add ``UnitNo.hydstra`` and ``UnitNo.wilma`` attributes

- Add `sa_gwdata.parse_well_ids(plaintext)` to parse well IDs from plain text
- Add `ObsNo` and `UnitNo` classes for ID parsing