[BUGFIX] Rootline relation overlay does not work for translated pages

Overlays for the relation fields of a page in the rootline,
introduced with the rootline class refactoring, do not work for
translated pages.
The problem is that the language overlay for the rootline is done outside
the RootlineUtility, or former PageRepository, and therefore also never
has been cached.

Use Rootline utility to do that Job and benefit fom caching, too.

Change-Id: If32830b384b08e189d155532aee7281b040b7dd5
Resolves: #42029
Releases: 6.0
Reviewed-on: http://review.typo3.org/16540
Reviewed-by: Helmut Hummel
Tested-by: Helmut Hummel