Svvamp

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* ``RuleExhaustiveBallot``, ``RuleCondorcetAbsIRV`` and ``RuleCondorcetVtbIRV``: accelerate counting the ballots. This
also speeds up ``RuleIRV``, which relies directly on ``RuleExhaustiveBallot``.

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* The option ``sort_voters`` in ``Profile`` and related classes (such as ``GeneratorProfile`` and its subclasses) is
now False by default.
* ``Rule``: accelerate exact IM, UM and CM (generic exact algorithms for ranking-based rules).
* ``RuleBaldwin``: accelerate counting the ballot and computing the winner (especially useful for exact UM).
* ``RuleSTAR``: accelerate TM.
* ``RuleICRV``, ``RuleIRVAverage``, ``RuleSmithIRV``, ``RuleTideman``, ``RuleWoodall``: accelerate CM.
* Improve the management of options in ``RuleExhaustiveBallot`` and ``RuleIRV``. In some (common) cases, it accelerates
the computation of related voting rules (``RuleCondorcetAbsIRV``, etc).

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* Fix bug: ``preferences_rk`` was an array of floats, it is now an array of integers.

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* Accelerate ``ProfileSubsetCandidates`` (used for IIA but also for some voting rules such as ``RuleTideman``).
* Add ``ProfileUM``. This is used to speed up the generic exact algorithm for UM in the case of voting rules based
on rankings.
* ``RuleTideman``: accelerate counting the ballot and computing the winner (especially useful for exact UM).
* Accelerate ``preferences_ut_to_matrix_duels_ut``.
* Accelerate ``matrix_victories_to_smith_set``.

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* ``RuleMaximin``: implement ``cm_option=faster``, which is as precise as ``fast`` to compute ``is_cm_``, less precise
to compute the bounds ``necessary_coalition_size_cm_`` and ``sufficient_coalition_size_cm_``, but a lot faster.

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* ``Profile`` now has a parameter ``preferences_borda_rk``. At initialization, it can be given instead of
``preferences_rk``.
* ``ProfileSubsetCandidates``: accelerate the initialization method.

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