Support more than one genre for an episode

[dagwieers]

This supports more than one genre in the XMLTV output.

VRT NU can have more than one category for a tv show episode or a movie.

[dagwieers]

Another option is that we deprecate genre and introduce genres which is always a list.

                    # NOTE: Backward compatibility with earlier format
                    if item.get('genre'):
                        program += ' <category>{genre}</category>\n'.format(
                            genre=cls._xml_encode(item.get('genre')))

                    if item.get('genres') and isinstance(item.get('genres'), list):
                        for genre in item.get('genres'):
                            program += ' <category>{genre}</category>\n'.format(
                                genre=cls._xml_encode(genre))

[michaelarnauts]

I prefer to keep it at genre, so checking if it's a list does the trick.