* Compute a custom score by the subQuery score and a number of ValueSourceQuery scores.

Subclasses can override this method to modify the custom score.

If your custom scoring is different than the default herein you should override at least one of the two customScore() methods. If the number of ValueSourceQueries is always < 2 it is sufficient to override the other {@link #customScore(int, float, float) customScore()} method, which is simpler.

The default computation herein is a multiplication of given scores:

                ModifiedScore = valSrcScore * valSrcScores[0] * valSrcScores[1] * ...