Make a set of input test images with GPL license

We need a set of small images which cover most image types which can be distributed under the GPL license:
- small jpeg image with exif data (and orientation != 1)
- image with iptc tags
- gif image (mode P with transparency)
- ... (Nadia, more needed?)

Stani will adapt the doctests afterwards, which are now failing because of missing images.

Also we need to create a 'golden set' to diff the output images of the acceptance test.