Remove results for domains that are no longer in the index

[exortech]

I believe that currently the index page continues to show every domain that previously had generated results even if that domain is no longer in the index.

I believe that we should remove those old results - or at least stop them from showing on the index page. Now that I sorted all of the domains, it's pretty apparent that there a bunch at the bottom that are no longer valid and should be removed: https://tracker.greenweb.org/index/doteco-domains/

[fershad]

Thanks @exortech.

I feel that domains that were once part of an index and have since been removed should still be represented on the index page. It would make sense to show them in a separate table at the bottom of the index under a heading "Archived domains" or similar.

I won't have time to work on something like this until December, but PRs are most certainly welcome in the interim.