bnc#882383: Do not ignore themeOverride for charts in .pptx

Otherwise wrong colors are displayed.

(cherry picked from commit 08818d8a45e034ad825c7fafbb76766f106f1d1d)

Conflicts:
	oox/source/drawingml/shape.cxx

Change-Id: I5d7444100355fdbc5fcd2aaa1c01202ace54312d
Reviewed-on: https://gerrit.libreoffice.org/10134
Reviewed-by: Markus Mohrhard <markus.mohrhard@googlemail.com>
Tested-by: Markus Mohrhard <markus.mohrhard@googlemail.com>