Support parsing input parametres from pyproject.toml config

[mbalatsko]

This PR adds possibility to set pip-licences input parameters from pyproject.toml file. The change made to be minimally invasive to project logic:

• All parameters configurable using CLI are configurable using pyproject.toml in the special section for pip-licences tool
• Inputs set in CLI have higher priority than pyproject.toml and can override them
• All different types of parameters parsing from toml and overriding by cli was tested in a separate test

Main motivation: #148 and I really love that in modern python packages you could configure all tools in pyproject.toml

[raimon49]

@mbalatsko Thank you! Very interesting suggestion.

Also, your implementation is considerate of existing users and looks very professional.

Toward merging this PR, I think it would be better if the README document has the [tool] table contents of the example TOML file and the specs when loaded.

[mbalatsko]

@raimon49 sure, I completely forgot to add it to README, will do!

[mbalatsko]

@raimon49 please take a look, should be all there

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 99.13%. Comparing base (b3a3d87) to head (ee26a1c).

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #200      +/-   ##
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+ Coverage   99.12%   99.13%   +0.01%     
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  Files           1        1              
  Lines         457      465       +8     
==========================================
+ Hits          453      461       +8     
  Misses          4        4              

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[raimon49]

@mbalatsko Perfect! I will ship to PyPI based on the merged master branch.

[raimon49]

Just shipped v4.5.0 and we can now use the features implemented in this PR.
https://pypi.org/project/pip-licenses/4.5.0/