Support for ordering investigation contacts

````
:I311   a                     isa:Investigation ;
        tb:hasAuthor          <http://example.net/U106> , <http://example.net/U120> , <http://example.net/U348>;
        isa:hasOrderedAuthor  [ tb:hasAuthor          <http://example.net/U106> ;
                                isa:hasOrderedAuthor  "1"^^xsd:int
                              ] ;
        isa:hasOrderedAuthor  [ tb:hasAuthor          <http://example.net/U120> ;
                                isa:hasOrderedAuthor  "3"^^xsd:int
                              ] ;
        isa:hasOrderedAuthor  [ tb:hasAuthor          <http://example.net/U348> ;
                                isa:hasOrderedAuthor  "2"^^xsd:int
                              ] ;

````