Tombstone redirect forked apps to active release

This is about removing abandoned duplicates. Currently the maintainer will leave a note on their issue tracker or on the their Git repo, or maybe on the description of their appstore listing. Either way, it is problematic once someone maintaining a fork of that app also adds their release to the appstore under a different name. Very confusing.

Add the ability to re-direct an abandoned app listing, which has been actively forked by something actively maintained. This will avoid any confusion on part of the person viewing, who should not be considering abandoned and unsupported app releases.

- Add some sort of very visual warning to the listing.
- Encourage the user to re-direct to the current app.
- Or, force the user to re-direct to the current app.

See also
- #1475
- #412