Genieclust

* [Python and R] New function: `adjusted_asymmetric_accuracy`.

* [Python and R] Implementations of the so-called internal cluster
validity measures discussed in
DOI: [10.1016/j.ins.2021.10.004](https://doi.org/10.1016/j.ins.2021.10.004);
see our (GitHub-only) [CVI](https://github.com/gagolews/optim_cvi) package
for R. In particular, the generalised Dunn indices are based on the code
originally authored by Maciej Bartoszuk. Thanks.

Functions added (`cluster_validity` module):
`calinski_harabasz_index`,
`dunnowa_index`,
`generalised_dunn_index`,
`negated_ball_hall_index`,
`negated_davies_bouldin_index`,
`negated_wcss_index`,
`silhouette_index`,
`silhouette_w_index`,
`wcnn_index`.

These cluster validity measures are discussed
in more detail at <https://clustering-benchmarks.gagolewski.com/>.

* [BACKWARD INCOMPATIBILITY] `normalized_confusion_matrix`
now solves the maximal assignment problem instead of applying
the somewhat primitive partial pivoting.

* [Python and R] New function: `normalizing_permutation`

* [R] New function: `normalized_confusion_matrix`.

* [Python and R] New parameter to `pair_sets_index`: `simplified`.

* [Python] New parameters to `plots.plot_scatter`:
`axis`, `title`, `xlabel`, `ylabel`, `xlim`, `ylim`.

* [GENERAL] A paper on the `genieclust` package is now available:
M. Gagolewski, genieclust: Fast and robust hierarchical clustering,
SoftwareX 15, 100722, 2021, DOI:
[10.1016/j.softx.2021.100722](https://doi.org/10.1016/j.softx.2021.100722).

* [Python] `plots.plot_scatter` now uses a more accessible default palette
(from R 4.0.0).

* [Python and R] New function: `devergottini_index`.

* [R] Use `mlpack` instead of `RcppMLPACK` (72).
This package is merely suggested, not dependent upon.

* [Python] Require Python >= 3.7 (implied by `numpy`).

* [Python] Require `nmslib`.

* [R] Use `RcppMLPACK` directly; remove dependency on `emstreeR`.

* [R] Use `tinytest` for unit testing instead of `testthat`.

* [BUGFIX] [R] Fix build errors on Solaris.

* [BUGFIX] [Python] Add code coverage CI. Fix some minor inconsistencies.
Automate the `bdist` build chain.

* [R] Update DESCRIPTION to meet the CRAN policies.