[FEATURE] Add stdWrap feature: addPageCacheTags

This feature comes after feature freeze for 4.7 but accidently it was
already mentioned in the release notes while not being implemented yet.

Release notes mention that the new stdWrap.cache feature (#34299)
stores cache tags that can be flushed by tag from TCEmain.clearCacheCmd
with feature #34352.

As stdWrap.cache stores tags into cache_hash and not into cache_pages
the feature mentioned in the release notes does not work that way.

But nevertheless that would be a handy feature and so I suggest to
add stdWrap.addPageCacheTags = pagetag1,pagetag2,pagetag3

To distinguish these tags being written to cache_pages instead of
cache_hash I'd suggest to not have this feature inside "cache." but
as a separate configuration option "addPageCacheTags".

See http://forge.typo3.org/issues/34403 for some more details.

Including the other cache (tag) related features this completes a set
of handy tools to handly cache tags in a very flexible way.

Change-Id: Ida42937356644f8ea1c27cecdf1e8252182b06ee
Resolves: #34403
Releases: 6.1
Reviewed-on: https://review.typo3.org/9294
Reviewed-by: Steffen Ritter
Tested-by: Steffen Ritter
Reviewed-by: Christian Kuhn
Tested-by: Christian Kuhn