Filter out editors, they are now seen as authors

[Michael Cochez]

At the moment, the editors of a volume are also included in the author list. They need to be filtered out.

    -   creatorType: author
        firstName: Michael
        lastName: Cochez
    -   creatorType: editor
        firstName: Ingo
        lastName: Frommholz

Would result in both being listed as author.

[Michael Cochez]

Fixed in 2daf1c8