private double getSignificance(BlockItem blockItem) {
        if (blockItem instanceof TermItem) return ((TermItem)blockItem).getSignificance();
        else return ((PhraseSegmentItem)blockItem).getSignificance();
    }
Replaces query terms with their stems

@author Mathias Lidal
@author bratseth
@author Steinar Knutsen
container-search/src/main/java/com/yahoo/prelude/querytransform/StemmingSearcher.java