Add nichart mode

[tsalo]

Closes none.

Changes proposed in this pull request

• Add a "nichart" mode that matches how the NiChart project is processing its data.
• Make the default values for --smoothing and --min-coverage "auto", since "nichart" mode has defaults that differ from the current defaults.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 79.04%. Comparing base (7694faa) to head (cfa1385).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1320      +/-   ##
==========================================
+ Coverage   78.96%   79.04%   +0.08%     
==========================================
  Files          59       59              
  Lines        7383     7412      +29     
  Branches      957      961       +4     
==========================================
+ Hits         5830     5859      +29     
  Misses       1261     1261              
  Partials      292      292              

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