Provide `min_score` and `max_score` values in the Package API endpoint

[tdruez]

A "range string" is not an actional data point, it's not conveniant to be used for sorting, filtering, etc... A better data in the API would be the min_score and max_score, as the range string can easily be computed from those 2. We want to make sure this is available in the bulk_search as well.