This bug fixes the DOCX import and export filters, adds a new property
to the document model and updates the UNO API.
There is no need to add layout \ UI updates, because in Word
the only way to turn this on\off is using a simple button,
and there is no way to control the shading color itself.
However, ODF import \ export filters should be updated in a future
commit.

Conflicts:
	sw/qa/extras/ooxmlexport/ooxmlexport.cxx

Change-Id: I1d34cec79289e38c08e42a4c6265d998e1edfdef
Reviewed-on: https://gerrit.libreoffice.org/4452Reviewed-by: Miklos Vajna <vmiklos@suse.cz>