GH-2371: Add tooltip to progress bars (via title attr)

[kinow]

GitHub issue resolved #2371

Pull request Description:

Adds tooltips in case you have very long list and the text is not visible in the progress bars.

Here's a preview of the tooltip (dark tooltip, over one of the progress bars, mouse pointer not displayed).

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• Tests are included.
• Documentation change and updates are provided for the Apache Jena website
• Commits have been squashed to remove intermediate development commit messages.
• Key commit messages start with the issue number (GH-xxxx)

By submitting this pull request, I acknowledge that I am making a contribution to the Apache Software Foundation under the terms and conditions of the Contributor's Agreement.

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See the Apache Jena "Contributing" guide.

[kinow]

And I think it should be OK to skip tests for this one (not sure how hard/easy it'd be to test that the tooltip appears... we could test for the title attribute if others want...)

[kinow]

Used wrong GH issue 😮‍💨 give me a sec to fix that...

[kinow]

Fixed, only the branch name remains gh-2370, but I think that's harmless. Sorry.