Merge branch '12-add-improve-skins' into 'master'

android/gradle.properties

assets/icons/skin_food.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_9.png

assets/skins/food_1.png

assets/skins/food_2.png

assets/skins/food_3.png

assets/skins/food_4.png

assets/skins/food_5.png

assets/skins/food_6.png

assets/skins/food_7.png

assets/skins/food_8.png

assets/skins/food_9.png