private void setupAutomatonFile(String phraseAutomatonFile) {
        if (phraseAutomatonFile == null || phraseAutomatonFile.trim().equals("")) {
            //no file, just use dummy matcher
            phraseMatcher = PhraseMatcher.getNullMatcher();
        } else {
            //use real matcher
            phraseMatcher = new PhraseMatcher(phraseAutomatonFile,true);
        }
    }
Detects query phrases. When a phrase is detected in the query,
the query is mutated to reflect this fact.

@author bratseth
@author Einar M R Rosenvinge
container-search/src/main/java/com/yahoo/prelude/querytransform/PhrasingSearcher.java