n#862516: Remember slides sorter view setting.

Keep the number of slides per row when moving across tabs.

Change-Id: I316dac87c9dc8c88149b510f93be88940d91d98c
Reviewed-on: https://gerrit.libreoffice.org/8545
Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>