PUBLIC MARKS from nhoizey with tags c & rdf

This utility uses the photos.getInfo API to interpret the description fields and the tags for a photo URI into RDF triples. If raptor is present, it will be used to provide proper serializing to RDF rather than the built in and hacky ntriples/turtle output. Machine tags when they are found are scanned for xmlns:prefix=uri and then all other machine tags with that prefix turn into triples. Several prefixes are also pre-defined by the library to automatically get turned into triples without an xmlns, such as blue:, cell:, filter: and geo:. Non-machine tags are not yet interpreted.