code: protected String explainScoreCombination(double[] multiScore) {
  		StringBuffer buf = new StringBuffer("");
  		PrintfFormat fmt = new PrintfFormat(" %.3f");
  		buf.append("field-level scores [");
  		for (int i=0; i<multiScore.length; i++) {
  			buf.append(fmt.sprintf(multiScore[i]));
  		}
  		buf.append("] Average score:");
  		buf.append(fmt.sprintf( scoreCombination(multiScore) ));
  		return buf.toString();
  	}
docs: Explain how to combine the scores for each primitive distance
  function on each field.