opam.ocaml.org integration

This should prepare ocaml.org to generate a template for opam.ocaml.org and host the necessary assets. No user-visible changes should occur after application.

Please review.
I didn't want to list all the dependencies/didn't look up how they are tracked through mpp files. The generation happens so quickly, I don't think it's a problem to re-run it even when everything is up-to-date.