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

assets/skins/aventure_1.png

assets/skins/aventure_2.png

assets/skins/aventure_3.png

assets/skins/aventure_4.png

assets/skins/aventure_5.png

assets/skins/aventure_6.png

assets/skins/aventure_7.png

assets/skins/aventure_8.png

assets/skins/aventure_found.png

assets/skins/aventure_unknown.png

assets/skins/default_1.png

assets/skins/default_2.png

assets/skins/default_3.png

assets/skins/default_4.png

assets/skins/default_5.png

assets/skins/default_6.png

assets/skins/default_7.png

assets/skins/default_8.png

assets/skins/default_found.png

assets/skins/default_unknown.png