Add skins "aventure", "nature" and "items"

resources/ui/skins/items/6.png

resources/ui/skins/items/7.png

resources/ui/skins/items/8.png

resources/ui/skins/items/found.png

resources/ui/skins/items/unknown.png

resources/ui/skins/nature/1.png

resources/ui/skins/nature/2.png

resources/ui/skins/nature/3.png

resources/ui/skins/nature/4.png

resources/ui/skins/nature/5.png

resources/ui/skins/nature/6.png

resources/ui/skins/nature/7.png

resources/ui/skins/nature/8.png

resources/ui/skins/nature/found.png

resources/ui/skins/nature/unknown.png