Port kiwix-tools to docoptcpp

[mgautierfr]

Currently, kiwix-tools are using getopt to parse command line.

However, this library is a unix tool and is not available on Windows [1].
As other projects (zim-tools) are using docoptcpp and it is packaged by kiwix-build, it would be nice to use docoptcpp in kiwix-tools too.

This way, we would use only one dependency to parse command line and it would simplify the compilation on Windows.

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[1] getopt is not really complex, it would be possible to compile it on Windows, but it means find the right upstream project, probably build a meson buildsystem (as Makefile is difficult on Windows) and integrate it in kiwix-build.

[kelson42]

@mgautierfr I guess you have implemented this feature with #695 and therefore this issue should be closed?

[mgautierfr]

Yes it is. I don't know why it haven't been closed. We have a commit with a "fix ..."

It has to be in the PR description, not only for me!