DOCX import sends 'table cell redline' to SW core, and core stores it

This patch adds support in the DOCX importer for the 'table cell redline'
to be sent from the DOCX importer, using UNO (as a property of the
table cell) to the SW core. Once it reaches the 'table cell' - the
'set property' detects this property - and creates an
'SwTableCellRedline' object for it, and adds it to the
'SwExtraRedlineTbl' object.

Change-Id: Iba038f4109d5505b94cea548e73c614b5cc1b637
Reviewed-on: https://gerrit.libreoffice.org/7875
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Miklos Vajna <vmiklos@collabora.co.uk>