add utility routine to return the phrase tree associated with a sentence.
add utility routine to return the phrase tree associated with a sentence.

anitzkin/relex,leungmanhin/relex,linas/relex,rodsol/relex,leungmanhin/relex,linas/relex,AmeBel/relex,rodsol/relex-temp,opencog/relex,ainishdave/relex,anitzkin/relex,rodsol/relex-temp,williampma/relex,rodsol/relex-temp,AmeBel/relex,leungmanhin/relex,rodsol/relex,virneo/relex,anitzkin/relex,williampma/relex,virneo/relex,williampma/relex,rodsol/relex-temp,ainishdave/relex,ainishdave/relex,virneo/relex,rodsol/relex-temp,virneo/relex,rodsol/relex,anitzkin/relex,linas/relex,anitzkin/relex,AmeBel/relex,rodsol/relex,williampma/relex,opencog/relex,ainishdave/relex,opencog/relex