Categories, recipes and ingredients now saved in hashmap together with their associated code and a whole bunch of refactoring to go along with it. TypeAdapters for Recipes, NutritionTables and Categories. Saving and retrieving Recipe, NutritionTable and Category to / from JSON works (see tests).

improved add-methods and knew method to check csv for other measurements than g and convert them to gram

testing shopping list, modified RecipeComponent interface: added a new method getMeasurement(). fixed logging

implemented algorithm to calculate nutrition tables for recipes from their ingredients -> added tests.
implemented equals() method for NutritionTable -> added tests.

slight refactoring...

changed Categories to CategoryManager and added IngredientManager with respective methods (partly moved from RecipeManager to IngredientManager)