Refactor the Question Answering Module Code

Description: In this deliverable I worked on refactoring the code for the Question Answering module in Yioop. I moved the entire code so that it is locale specific. I was able to remove the QuestionAnswer Extractor class which was hosting all the code for the Question Answering Module. The refactoring may helpin improving the efficiency of ths system. It also makes adding similar module for other languages easy as we just have to make chages to that particular locale.