Added basic CommonsKMLExtractor and reloaded the ontology to include a property to store them.
Updated Datatype to rdf:XMLLiteral.
Modified CommonsKMLExtractor so that the subject is the image being overlaid, not the overlay file itself.
Added CommonsKMLExtractor to default commons extraction.
Merge pull request #264 from gaurav/feature/commonskmlextractor

CommonsKMLExtractor