Mycroft-core: Pocketsphinx: Fallback to english model if language specific model doesn't exist

[forslund]

When using a pocketsphinx wakeword mycroft tries to load a language specific model. If the model doesn't exist the load fails. (report on the forums)

This should be handled by using a fallback mechanism, so if no language specific model exists it should log a warning and fallback to using the english model that is included in mycroft-core.

At L105 in hotword_factory.py a line to set the model to the default en-us should be added.

The code will look something like

        if not exists(model_file):
            LOG.error('PocketSphinx model not found at ' + str(model_file))
            model_file = join(RECOGNIZER_DIR, 'model', 'en-us', 'hmm')

[katridi]

I can take it