Normal shapes have a TextFitToSize property for this, but table cell
content has to be scaled manually, as the rendering has no automatic
support for them. Luckily the file format has the info we need to scale
at import time.

Change-Id: Ibbcc4b8685995261536cce88b8c0774e148f708e
Reviewed-on: https://gerrit.libreoffice.org/60880Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins