The current TYPO3 Core includes different types of caches. There are
system-related caches (class loading cache, configuration cache,
l10n_cache, extbase_object, extbase_reflection etc.) and
frontend-related caches (chash cache, page cache, page section
cache).

The patch introduces the possibility to group caches. The core uses
two groups "pages" with all page-related caches, and "system" that
is used for compile-time caches and configuration caches.

The new API is now used to be more flexible inside DataHandler
clear_cacheCmd without having hooks, as the Cache Manager is used
to clear all caches inside one hook.

!!! The "Clear all caches" command does not flush caches for
system-related caches anymore. Only "Clear Configuration Cache" or
inside the install tool in the backend removes all the system caches.

A new userTSconfig option is used to non-admins to be allowed to
clear the system caches.

Resolves: #54991
Releases: 6.2
Change-Id: I...