shopping list type adapter

src/main/java/mi/hdm/filesystem/FileManager.java

src/main/java/mi/hdm/shoppingList/ShoppingList.java

src/main/java/mi/hdm/typeAdapters/MealPlanTypeAdapter.java

...ain/java/mi/hdm/typeAdapters/ShoppingListTypeAdapter.java

src/test/java/mi/hdm/filesystem/JsonTest.java

src/test/java/mi/hdm/recipes/ValidObjectsPool.java