Icepool

* `MultisetExpression.map_counts()` now accepts multiple arguments.
* `MultisetExpression.keep_outcomes()` and `drop_outcomes()` now accept an expression as an argument.
* `MultisetExpression.highest_outcome_and_count()` now returns the min outcome if no outcomes have positive count.

* `highest`, `lowest`, and `middle` can now take a single iterable argument.
* Add `all_straights` evaluation.
* `all_counts` and `all_straights` now output sizes in descending order.
* Harmonize method and free function versions of `map`. Both now allow extra arguments and repeat.
* Rename `filter_counts` to `keep_counts`.
* `expand` evaluator now allows order to be set.
* Experimental `compair` evaluation.

* Add HTML and BBCode options for population formatting.
* Renamed `apply` to `map` and the decorator version to `map_function`.
* The above now uses `guess_star`.
* Add default of 1 die for `Die.pool()`.

Fix mathematical bug in `Die.reroll` for limited depth.

Retired implicit elementwise operations on tuples. This is now handled by a new explicit `Vector` container.
`cartesian_product()` is replaced by two new functions: `tupleize()` and `vectorize()`.
These compute the Cartesian product and produce a `tuple` or `Vector` respectively (or a die/deck thereof).

The `Again` symbol is now used without parentheses. The name of the underlying type is now `AgainExpression`.

`die.zero()` now multiplies all outcomes by `0` to determine the zero-outcome rather than using the default constructor.
This allows it to work with `Vector`'s elementwise operations while still producing the expected result for
tuples, strings, etc.

Retired the linear algorithm for comparators for `Die`. While the quadratic algorithm is slower, it allows for non-bool outputs.

`die.tuple_len()` renamed to `common_outcome_length`. Now applies to all sized outcome types.

* Counts type `Qs` is now invariant with more detailed typing in `Deal`.