Verified with color, gradient, bitmap for:
Chart Title in DOCX, XLSX and PPTX.

Also verified with gradient, bitmap for
Chart Legend, Plot Area, Dataseries and Background
in DOCX, XLSX and PPTX.

Change-Id: I15d29f3ca2d75f45f612766b635d50a29d8551ae
Reviewed-on: https://gerrit.libreoffice.org/57880
Tested-by: Jenkins
Reviewed-by: Bartosz Kosiorek <gang65@poczta.onet.pl>