Refactor stereo reconstruction

[YoshikiOhtani]

This pull request includes some minor refactoring of the code of the stereo parameters reconstruction. Here is a brief summary of the changes:

• changed the option name of the function stereo_reconstruction from magic_only to magic_only_analysis (but the argument name --magic-only used when running the script does not change).
• cleaned up the code of checking the angular distance of the pointing directions
• modified the logger information display

I checked that the outputs do not change before and after the refactoring and so it would be safe to merge now, but again I keep it here a few days so any comments or requests are very welcome.

[aleberti]

Also here changes look good, no particular comment from my side

[YoshikiOhtani]

I just pushed a commit about the change of an output file name when using the --magic-only argument to clarify from name that the data are processed by only MAGICs.

[YoshikiOhtani]

@aleberti I also modified the stereo reco script by following suggestions by flake8 (max-line-length = 90), and run isort and black. It would be much appreciated if you could check it and merge to the master if it looks OK to you. Thanks!