Add publisher-name as a filter (currently it's only a facet)

[ssmulyan]

For example, University Press of Colorado would like to know all the Books that JSTOR has registered on their behalf.

I can facet JSTOR's 10.2037 prefix by publisher-name value
http://api.crossref.org/prefixes/10.2307/works?facet=publisher-name:*
which shows that there are currently 519 items registered where <publisher_name>University Press of Colorado</publisher_name> was included in the metadata

Since <publisher_name> is only supported in the Books and Conference Proceedings schemas, I don't need to limit by content type.

But, there's no way to retrieve the specific 519 items with that publisher name value.

e.g.
http://api.crossref.org/prefixes/10.2307/works?filter=publisher-name:University%20Press%20of%20Colorado
returns
"type": "filter-not-available",
"value": "publisher-name",
"message": "Filter publisher-name specified but there is no such filter for this route...