Fix searching resources with multiple authors (closes #77)

Deployed for testing at http://api.lobid.org/

Samples:

http://api.lobid.org/resource?author=131392786
http://api.lobid.org/resource?author=Neil+Eric+Schore+(1948-)
http://api.lobid.org/resource?author=Kurt+Peter+C.+Vollhardt+(1946-)