Update for package version ranges

[pombredanne]

Given a vuln that has a stored version range per #140, we need to design a way to update the DB for version ranges when we get new and updated package versions (#142) or vulnerablities.

[TG1999]

Being done in https://github.com/nexB/vulnerablecode/blob/main/vulnerabilities/improvers/valid_versions.py, closing this