1) Write endParaRPr so that PowerPoint display them properly.
2) Original design forbid properites with default value to be exprted, now fixed.
3) Automatic colors are written as white or black based on
   whether background is dark.

Note that tdf#77881,tdf#80520,tdf#89525 depend on this.

Change-Id: I255c16f35149b738be2daf2800b1c90389f2c7cf
Reviewed-on: https://gerrit.libreoffice.org/17472Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Norbert Thiebaud <nthiebaud@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/19862Reviewed-by: Katarina Behrens <Katarina.Behrens@cib.de>
Tested-by: Katarina Behrens <Katarina.Behrens@cib.de>
(cherry picked from commit 0b5e3885)