[TASK] Move non-public files to typo3temp/var/

Add a subdirectory typo3temp/var/ (by default) which
contains all files which should never be accessible
for the web user.

In the future, this option should be configurable so it can
be put outside of the document root (e.g. via an
environment variable).

Resolves: #72479
Releases: master
Change-Id: Ia2e425a2ff55deac91c02b829c73036478995b0b
Reviewed-on: https://review.typo3.org/45505


Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Susanne Moog <typo3@susannemoog.de>
Tested-by: Susanne Moog <typo3@susannemoog.de>