[FEATURE] Info ViewHelpers for page and content information array

Adds ViewHelpers ``f:info.page`` and ``f:info.content`` which return
or assign content or page information arrays respectively depending
on usage of the ``as`` argument as known from other helpers.

Change-Id: Idfa5b68b37e926593072ddf75e6d143a2c5037f8
Releases: master
Resolves: #38942
Reviewed-on: https://review.typo3.org/46473


Reviewed-by: Frank Naegler <frank.naegler@typo3.org>
Tested-by: Frank Naegler <frank.naegler@typo3.org>
Reviewed-by: Jan Helke <typo3@helke.de>
Tested-by: Jan Helke <typo3@helke.de>
Reviewed-by: Markus Klein <markus.klein@typo3.org>
Tested-by: Markus Klein <markus.klein@typo3.org>