Use Rummager as search backend

Replacing soon to be decommissioned Finder API which is still in use for
sharing schemas.

[Trello ticket](https://trello.com/c/5Xlpt8Mn/306-make-finder-frontend-use-rummager-for-results-3)
....ew. I know I was watching over your shoulder a little while you wrote this, but this still seems disgusting. Is there no way we can make `schema_hash` accessible without having to reach in and yank it screaming from `schema_attributes`?