Fix a mistake in a test method name
Fix bug on Recline's CKAN backend.

I created a PR with this fix at
https://github.com/okfn/recline.backend.ckan/pull/5.
We're able to filter the data now

I created a new .search_sql() on Recline's CKAN backend because, in the future,
we'll want to create multiple filters on the same field. The DataStore API
doesn't support that directly, unfortunately.