[CLEANUP] Shrink images

Image files (jpeg and png) shipped in the core are optimized.
Images within ./contrib are ignored.

Resolves: #63544
Releases: master
Change-Id: Id42fdf8f6d44880b4008eecb2a85015655837836
Reviewed-on: http://review.typo3.org/34978
Reviewed-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Tested-by: Mathias Schreiber <mathias.schreiber@wmdb.de>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>