Add reusedPropertyAs to PropertyValueReuse  #6

Now we can specify from which resource we reuse which property value, but this does not help with the interpretation of what that property represents, expecially when e.g. in one vocabulary titles are rdfs:label and in another skos:prefLabel. DSV-DAP prescribes, what is the label property and what is the definition of a Term Profile, so it cannot be viewed as "reuse as the same property as in the source". What is missing is "reusedPropertyAs" which would contain skos:prefLabel for labels and skos:definition for definitions, in compliance with DSV-DAP, clarifying the interpretation of the property value resource in the DSV-DAP RDF representation.