Use fix_random_seed in train NER

[lizgzil]

The pipeline is not deterministic. Fix this in prepare_model in ner_spacy.py with

from spacy.util import fix_random_seed

def prepare_model(self):
        """
        Prepare a Spacy model to have it's NER component trained
        """
       fix_random_seed(0)
        self.nlp = spacy.blank("en")