RDF serializer fix
- implement support for Rdf conversion of statements with properties
which have MonolingualText as primitive type
add licence header
implement translation from wikidata language encoding to BCP 47
add test for MonolingualTextValueConverter
remove space character from JSON datatype IRI
Use one method to convert MTV values to RDF (not two different ones)
Work with JSON dump by default
Guard against properties having been deleted since dump (no datatype)
Merge pull request #99 from Wikidata/monolingualTextValueSupportBugFix

Monolingual text value support in RDF export