n#821567: Import PPTX background images with table-name.

Ported from 2ec4d410de5bd98527336a9dc49abb76656373df

Change-Id: I19cefa3097d8a7c2da057089efb52ec8fd45b2b0
Reviewed-on: https://gerrit.libreoffice.org/8544
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>