New functionality: --replace-headers

[esimpsons3ti]

This pull request will introduce the new feature, --replace-headers. This command line argument allows the user to change the names of columns via a user-provided text file. For example, the contents of this file can be:

pds:Product_Observational/pds:Identification_Area<1>/pds:logical_identifier<1>,LID
pds:Product_Observational/pds:Identification_Area<1>/pds:version_id<1>,VID
pds:Product_Observational/pds:Identification_Area<1>/pds:title<1>,Title

and it will replace the XPath with the given replacement string. This command can be applied to both index files and header files.

Fixes #21

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 100.00%. Comparing base (0de3011) to head (ffdb3c6).
Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main       #45      +/-   ##
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+ Coverage   96.34%   100.00%   +3.65%     
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  Files           1         1              
  Lines         602       631      +29     
  Branches      124       132       +8     
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+ Hits          580       631      +51     
+ Misses         17         0      -17     
+ Partials        5         0       -5     

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[rfrenchseti]

This seems to do what I was hoping for. One small thing is if you have a blank line in your mapping file, it reports it as an error. It would be nice to skip over blank lines so people can organize their field renaming with gaps between them. As an added feature it would be nice to allow comment lines starting with "#" that are ignored. This already works for limit-xpaths files, probably just because there will never be an XML tag that starts with "#" so it never matches.

[rfrenchseti]

Shouldn't say "an index".

[rfrenchseti]

Also really df and index are redundant fields. You can't specify index=True without also specifying df. I would delete the index argument entirely, and just check to see if df is None. However, at that point, df and xpaths are redundant - you must specify one or the other but not both. So really you just want a single argument called something like df_or_xpaths. Then in the code you can say if isinstance(df_or_xpaths, pandas.DataFrame):