Add search and pagination for DocsR (/#SnapName/docs)

There is a page on stackage.org/SnapshotName/docs which lists all modules available for all packages in a particular snapshot. It has a lot of content and is very expensive. It takes ~10s for me to load on my local clone of stackage. Suggesting to disable it, so we can take the load of stackage.org as a follow up to #295

This issue is very similar to #299 in spirit, so anyone relying on this page feel free to submit a PR with pagination and a search form to make loading of that page acceptable.