Support counter-poise calculations in Python API

[awvwgk]

Closes #122

[codecov]

Codecov Report

Attention: Patch coverage is 77.16535% with 29 lines in your changes missing coverage. Please review.

Project coverage is 66.22%. Comparing base (3a50cbd) to head (36c3671).
Report is 37 commits behind head on main.

Files with missing lines	Patch %	Lines
python/dftd3/interface.py	56.75%	16 Missing ⚠️
python/dftd3/library.py	86.25%	11 Missing ⚠️
src/dftd3/output.f90	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main     #128       +/-   ##
===========================================
+ Coverage   48.63%   66.22%   +17.58%     
===========================================
  Files          34       34               
  Lines        3707     4625      +918     
  Branches     1518     1589       +71     
===========================================
+ Hits         1803     3063     +1260     
+ Misses       1207      679      -528     
- Partials      697      883      +186     

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