FisherFaceRecognizer added

Fisher Face Recognizer added in FaceRecognizer class.

Usage:

        f = FaceRecognizer()
        imgs1 = ImageSet(path/to/images_of_type1)
        labels1 = [0]*len(imgs1)
        imgs2 = ImageSet(path/to/images_of_type2)
        labels2 = [1]*len(imgs2)
        imgs3 = ImageSet(path/to/images_of_type3)
        labels3 = [2]*len(imgs3)
        imgs = imgs1 + imgs2 + imgs3
        labels = labels1 + labels2 + labels3
        f.train(imgs, labels)
        img = Image("some_image_of_any_of_the_above_type")
        print f.predict(img)

        Save Fisher Training Data
        f.save("trainingdata.xml")

        Load Fisher Training Data and directly use without trainging
        f1 = FaceRecognizer()
        f1.load("trainingdata.xml")
        img = Image("some_image_of_any_of_the_above_type")
        print f1.predict(img)

        Use CSV files for training
        f = FaceRecognizer()
        f.train(csvfile="CSV_file_name", delimiter=";")
        img = Image("some_image_of_any_of_the_type_in_csv_file")
        print f.predict(img)