GH-2462: Fuseki reload configuration

[afs]

GitHub issue resolved #2462

Pull request Description: Provide reload of the config.ttl with zero interruption of service.

• some clean-up done while working on this PR.
  The logging support code changes better isolate the logging implementation specific functions.

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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)

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[kinow]

Code is looking good! Had a quick go-through and found nothing that seemed wrong.

Any plans to expose it in the UI too, @afs? Like the backup/delete actions, in the management part of the UI? Or will it be only available if the user or admin prepares the request and runs it directly from command-line or some other HTTP client?

[namedgraph]

Is this available in jena-fuseki-main?

[namedgraph]

And can this feature be used to add new datasets?

[afs]

Any plans to expose it in the UI too, @afs? Like the backup/delete actions, in the management part of the UI? Or will it be only available if the user or admin prepares the request and runs it directly from command-line or some other HTTP client?

This discussion is showing that this is a big area. This PR isn't as grand as that.
It would be good to have admin UI to be able to do this.

That would be a reason to split the UI in two - admin and workbench. But again we can have big plans and we need tio have a way to creep up on them.

[afs]

Is this available in jena-fuseki-main?

This PR is open and not finished. The commit log for the codebase shows what's available.

And can this feature be used to add new datasets?

Yes - but not all types of datasets can be guaranted. Assemblers are too general.