Lossless image compression of png files using ImageOptim.
Saved 27KB out of 488KB. ~5% overall (up to 66% per file).

Change-Id: Ida48909411b02bbc6d355dc0678151089afabc26
Signed-off-by: Andrew <dent.ace@gmail.com>
Reviewed-on: https://gerrit.libreoffice.org/15393Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Adolfo Jayme Barrientos <fitojb@ubuntu.com>