0.0.21

• add new builtin methods: n_average, geometric_median, ties_sum_extended / add_difference_ties_extended, ties_sum_with_dropout / ties_with_dare, model_stock_for_tensor / model_stock_n_models
• add a new parameter vote_sgn to ties_sum / add_differenc_ties

credits to @6DammK9 for this contribution!