Image deduplication 2
Some more deduplication of image names (see issue #41).
I'm done with the list in my comment, except for the news.png file, of which I can only find one. It's very weird.
When I have time next, I will check the ones from Joubu's list. I also wanted to review the patron card chapter. I only redid the images that had duplicate names, but the whole chapter is worth revisiting I think.