ingest Hackage, the Haskell package repository (meta task)

We should extend archive coverage to the Hackage package archive for Haskell.

They have a package that knows the mirror structure and comes with a front-end CLI tool to keep a mirror up to date (on S3, but it can be hacked to work with a local mirror). It might be a useful starting point.

Thanks to Joey Hess and Clint Adams for their heads up and help on this!