Allow group specifications as integers or tuples

[mcara]

This PR fixes a bug reported in INC0189304 that, contrary to the documentation, setting group argument would result in a crash. In addition, now it is allowed to set group to a Python list of integers (extension numbers) and list of tuples of extension name and extension version ((extname, extver)).

[codecov]

Codecov Report

Patch coverage: 14.81% and project coverage change: -1.69% ⚠️

Comparison is base (d37ee76) 34.01% compared to head (124fe98) 32.33%.

❗ Current head 124fe98 differs from pull request most recent head ce5cac7. Consider uploading reports for the commit ce5cac7 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1612      +/-   ##
==========================================
- Coverage   34.01%   32.33%   -1.69%     
==========================================
  Files         126      159      +33     
  Lines       31124    35088    +3964     
  Branches     5794        0    -5794     
==========================================
+ Hits        10588    11347     +759     
- Misses      19333    23741    +4408     
+ Partials     1203        0    -1203     

Files Changed	Coverage Δ
drizzlepac/util.py	56.10% <6.25%> (+1.21%)	⬆️
drizzlepac/processInput.py	50.56% <80.00%> (+2.70%)	⬆️
drizzlepac/imageObject.py	68.21% <100.00%> (+5.80%)	⬆️

... and 129 files with indirect coverage changes

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[s-goldman]

Code looks good. If you could, however, please add explicitly in the docstring descriptions of the three inputs are and their allowed types, and what is returned.