Lossless optimisation of PNG files using ImageOptim app.
Many small savings ~1byte, total 8.8KB reduction.

Change-Id: Ieea65e7ae9ddfe9c103d58e155919dd1ce1a8270
Signed-off-by: Andrew <dent.ace@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/14888Reviewed-by: Jan Holesovsky <kendy@collabora.com>
Tested-by: Jan Holesovsky <kendy@collabora.com>