[FEATURE] Add base date for DateTimeViewHelper

This allows to use the full set of relative date formats
on a given base time:
http://www.php.net/manual/en/datetime.formats.relative.php

Resolves: #68022
Releases: master
Change-Id: Icf7c204b9c1d280805679b6edba7c03f575d936e
Reviewed-on: http://review.typo3.org/40843


Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>