ABWContentCollector: map dc.creator to meta:initial-creator
ABWContentCollector: map dc.creator to meta:initial-creator

librevenge's dc:creator stands for "last modified by" at multiple places
(LibreOffice, libvisio), meta:initial-creator is the author key.

Change-Id: If2641d973b1f436557e1fef355ae05863e25a3a5

LibreOffice/libabw,LibreOffice/libabw,LibreOffice/libabw