GH-2963: Cope with IPv6 address for the local machine

[afs]

GitHub issue resolved #2963

An accumulation of things during the build cycle:

Pull request Description:

• fix for The Jena build fails on a machine with only an IPv6 address #2963
• Test rename because two tests classes with the same name is confusing
• Improve the output of the IRI validator
• Better error messages for SPARQL protocol errors.
• Add a script to the Fuseki download to run Fuseki plain (missed in 5.3.0)

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• Commits have been squashed to remove intermediate development commit messages.
• Key commit messages start with the issue number (GH-xxxx)

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