BHL links require a scientific name

[nickdos]

Issue reported by Ely Wallis...

On the search results page, there is a "related searches" area at the top that includes a link to BHL. This search service only works for scientific names but there is a general "subject" search we can fall back to.

Plan is to take the query input and do a lookup against the BIE to see if there is a best match scientific name and use that (plus any synonyms ideally - BHL uses old names). If no match can be found, then we should change the param value for SearchCat to S (scientific name should use M).