CLI refactoring

[christophe-david]

This PR reworks the code for command line interface using click.

It makes the code much more simpler.

[codecov]

Codecov Report

Merging #405 (e6d3e26) into master (025dde5) will increase coverage by 0.60%.
The diff coverage is 12.31%.

@@            Coverage Diff             @@
##           master     #405      +/-   ##
==========================================
+ Coverage   90.29%   90.89%   +0.60%     
==========================================
  Files         200      201       +1     
  Lines        8195     8153      -42     
  Branches      854      854              
==========================================
+ Hits         7400     7411      +11     
+ Misses        641      586      -55     
- Partials      154      156       +2     

Impacted Files	Coverage Δ
src/fastoad/cmd/cli.py	0.00% <0.00%> (ø)
src/fastoad/cmd/cli_utils.py	0.00% <0.00%> (ø)
src/fastoad/cmd/api.py	90.75% <73.91%> (-1.18%)	⬇️

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[ScottDelbecq]

Thanks for this PR! click looks very convenient.
Does it enable to add tests for cli.py?

[christophe-david]

Does it enable to add tests for cli.py?

Yes, click comes with a small API for testing that should ease the process. I did not want to take the time now to ad these tests, since we did not have tests for the previous solution, but it should definitely been done.
Issue #407 now states that.