Returns all model paths in the model_dir.

def get_model_paths(model_dir):
    """Returns all model paths in the model_dir."""
    all_models = gfile.Glob(os.path.join(model_dir, '*.meta'))
    model_filenames = [os.path.basename(m) for m in all_models]
    model_numbers_names = [
        (shipname.detect_model_num(m), shipname.detect_model_name(m))
        for m in model_filenames]
    model_names = sorted(model_numbers_names)
    return [os.path.join(model_dir, name[1]) for name in model_names]