Documentation Updates

[syoon2]

This PR updates documentation, including:

• removing broken/outdated links in README
• adding module Javadocs in module-info.java
• improving exception documentations in Javadoc

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• I read and understood https://github.com/jgrapht/jgrapht/wiki/Become-a-Contributor
• I read and understood https://github.com/jgrapht/jgrapht/wiki/How-to-make-your-first-%28code%29-contribution
• I added unit tests (not applicable)
• I added documentation
• I followed the Coding and Style Conventions
• I have not modified HISTORY.md or CONTRIBUTORS.md
• I ensured that the git commit message is a good one

[syoon2]

This is a bit of a tangent: I think that the module-info.java and package-info.java files should also have the license header(s) put in. Adding them is not a part of this PR (didn't want to break any of your policies before checking first) but it is worth bringing up.

[jsichi]

Regarding the question of adding the license headers to the -info.java files, yes, that would be a good as a separate PR. If you do that, be sure to remove the exclusions in etc/jgrapht_checks.xml and etc/checkstyle_suppressions.xml.

Another tangent from there, it appears that jgrapht-unimi-dsi is missing from the list of updateOneModule calls in etc/updateCopyRightYear.sh. Also in etc/codeFormatter.sh.

[syoon2]

Regarding the question of adding the license headers to the -info.java files, yes, that would be a good as a separate PR. If you do that, be sure to remove the exclusions in etc/jgrapht_checks.xml and etc/checkstyle_suppressions.xml.

See #1215.

[jsichi]

Thanks!