[BUGFIX] Added missing workspace preview info

The workspace preview info got lost from TYPO3 4.5 to 4.6. This commit
readds the info and respects the same TypoScript config options.

Resolves: #77467
Releases: master, 8.7
Change-Id: Ie1696a5f86714c6ef9a61c10c41b0397abb95ab5
Reviewed-on: https://review.typo3.org/49740


Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>