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).

abstract class BaseController, figuring out dependency injection into JavaFX controllers, added enum View.java to get correct Scene object (with correct constructor)

added more validation to Recipe constructor, fixing bugs in RecipeSearch, tests for RecipeSearch. now adding full recipes to the shopping list

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)

added tests to categories: they should not be created with a name that is "", null and only be created with a color code where 0 <= code <= 0xFFFFFF