GH-3221 Fix SchemaDO._abstract URI

[fpotier]

The property URI should not have a leading underscore

GitHub issue resolved #3221

Pull request Description:

---

• 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.

---

See the Apache Jena "Contributing" guide.

[afs]

Thank you!

[fpotier]

@afs thanks for the reactivity!
Do you have any idea when this will be released?

[afs]

Do you have any idea when this will be released?

It is in the codebase now, and will be in a development snapshot in the next day or so.

The next official release is possibly mid-July, may be later. We don't give fixed dates because making a release takes volunteer time and it also depends on the state of development.