Consider using required phrases in license rule for ranking matches instead of filtering

[pombredanne]

Required phrases in license rules are used to filter out matches that do not have these required phrases present.
There are cases where this is filtering too many matches and we would need to systematically re-run a second level "unknown" license detection afterwards.

We should consider using the presence of "required phrases" in a match for ranking instead.
A simple approach is rank matches with required phrases present higher or highest, but not discard the matches that are missing some or all of the required phrases, so that we still return lower scored matches in these edge cases where the match may have been one of a kind and should not have been filtered early even if imperfect.