Minor hashCode/equals override improvements

[Neutius]

• Removed hashCode() override from Datum class - it does not override equals(), and should not override hashCode(). The isEqual() method could be renamed or rewritten to override equals, but is currently does not.
• Added hashCode() override to Unit class and Pair class.
• Added override annotations to Ellipsoid class for clarity.

[Neutius]

These checks on legal agreements are getting pretty annoying.

On the Eclipse site, it has a green check mark next to "Eclipse Foundation Project", and a red cross next to "Eclipse Foundation Specification Project". Underneath that, it says:

• Author(s) covered by necessary legal agreements: Gijs Van der Neut-Lamberink (sfcgijs@****.com)
• Failures: Anonymous (48245403+neutius@****.noreply) is not covered by the necessary legal agreements in order to proceed.

Apparently, the problem is I pulled from locationtech to my own fork to get up to date, it automatically includes that merge commit in this pull request, and the merge commit lacks the necessary legal agreements.

The only solution I can think of right now is deleting my fork, forking again, then committing again, then offer a pull request with a single commit.

I'm new to the FOSS community, and still getting used to GitHub. Is there a better solution?

Edit: the feedback from GitHub and Eclipse don't line up. According to GitHub, the merge commit is fine. I really don't get it.