Add support to display compat

[hesa]

With these commits the user can visualize the compatibility between licenses, with different output formats but dot being the recommended.

To create a png (attached) with compatibilities using all resources:

$ licomp-toolkit  -of dot display-compatibility GPL-2.0-only Apache-2.0 LGPL-2.1-only MIT > compat.dot
$ dot compat.dot -Tpng -o compat.png

Note: the blue dotted lines show inconsistency between the misc licomp reourses.

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To create a png (attached) with compatibilities using only https://github.com/hesa/licomp-reclicense:

$ licomp-toolkit -r licomp_reclicense  -of dot display-compatibility GPL-2.0-only Apache-2.0 LGPL-2.1-only MIT > compat-rl.dot
$ dot compat-rl.dot -Tpng -o compat-rl.png