CommonsKMLExtractor

This extractor identifies '/overlay.kml' files stored on the Commons as part of Geocoding Overlays (https://commons.wikimedia.org/wiki/Commons:Geocoding/Overlay) and associates the raw Keyhole Markup Language (KML, a form of XML) they contain as an rdf:XMLLiteral associated with the original resource.

This pull request updates the ontology as the CommonsKMLExtractor uses the new dbo:hasKMLData property, and closes gaurav#22.