Support multi value queries for nwbibsubject, nwbibspatial, subject, and medium

[fsteeg]

See #226

Deployed to staging, see:

• http://test.lobid.org/resource?subject=4066438-7,4077548-3&format=full
• http://test.lobid.org/resource?nwbibspatial=K%C3%B6ln,M%C3%B6nchengladbach&format=full
• http://test.lobid.org/resource?nwbibsubject=http://purl.org/lobid/nwbib%23s706230,http://purl.org/lobid/nwbib%23s704042&format=full
• http://test.lobid.org/resource?medium=http://rdvocab.info/termList/RDACarrierType/1018,http://rdvocab.info/termList/RDACarrierType/1010&format=full

[fsteeg]

Reassigning to myself to change boolean logic to OR, see https://github.com/hbz/lobid/issues/226#issuecomment-137380431.

[fsteeg]

Changed boolean logic to OR, deployed to staging, see:

• http://test.lobid.org/resource?subject=4066438-7,4077548-3&format=full
• http://test.lobid.org/resource?nwbibspatial=K%C3%B6ln,M%C3%B6nchengladbach&format=full
• http://test.lobid.org/resource?nwbibsubject=http://purl.org/lobid/nwbib%23s706230,http://purl.org/lobid/nwbib%23s704042&format=full
• http://test.lobid.org/resource?medium=http://rdvocab.info/termList/RDACarrierType/1018,http://rdvocab.info/termList/RDACarrierType/1010&format=full