Add group comparisons

[phobson]

So far:

• made some minor clean ups
• added infrastructure for general comparison tests (i.e., N > 2 groups)
• convert some cache'd DataCollection properties to methods so that we can pass options on to scipy.stats.<func>
• add some F-test and Kruskal-Wallis to DataCollection

Left to do:

• add Tukey HSD weirdness
• Add the Dunn test stuff

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 46.66667% with 24 lines in your changes are missing coverage. Please review.

Project coverage is 27.48%. Comparing base (d63b8b0) to head (6bf308d).
Report is 2 commits behind head on main.

❗ Current head 6bf308d differs from pull request most recent head c5c793f. Consider uploading reports for the commit c5c793f to get more accurate results

Files	Patch %	Lines
wqio/datacollections.py	52.63%	18 Missing ⚠️
wqio/features.py	0.00%	4 Missing ⚠️
wqio/viz.py	33.33%	2 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #188      +/-   ##
==========================================
- Coverage   28.02%   27.48%   -0.54%     
==========================================
  Files          11       11              
  Lines        1895     1899       +4     
  Branches      487      474      -13     
==========================================
- Hits          531      522       -9     
- Misses       1364     1377      +13     

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