This patch is implementing import of table styles (table-template).

Modified shared code: Added "background" to the cell styles export.

To make cell export properties map accessible by both export and import code,
moved from xmloff/source/table/XMLTableExport.cxx to xmloff/txtprmap.hxx.

To avoid export of default valued properties implemented XPropertyState for
SwXTextCellStyle

Change-Id: I8b4f12e4b51f478f8ce8fde1203cd4611d7ae852
Reviewed-on: https://gerrit.libreoffice.org/26721Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>