Update zenodo to be easy to use with astropy release procedures

[eteq]

This issue is specifically about the core package, but it's in astropy-project because it probably applies to anyone else who's using Zenodo for managing DOIs, etc.

• It's a bit opaque how Zenodo decides this, but however it's done, it appears the Zenodo entry is not associated with the shared astropy account. That should happen automatically somehow if possible when the hook is triggered.
• Newer versions of the Astropy Zenodo entry do not appear associated with older ones from before Zenodo had the "Versions" concept. We should see if this can be post-hoc fixed, but if not we should do something to associate them, if only links in the metadata on Zenodo.

[eteq]

I've sent a support request to Zenodo to try to fix the above.