fixed some getter methods -> got rid of writable references. better error messages. fixed bug in recipe manager where recipes were created in a wrong way (put name as key instead of code)

This reverts commit 2b0b34d1

moved HeaderController into new package. Now displaying NutritionTable in MealPlan. -> going to turn it into a component to reuse it in RecipeView. Introduced parallel search to RecipeSearch.

moved HeaderController into new package. Now displaying NutritionTable in MealPlan. -> going to turn it into a component to reuse it in RecipeView. Introduced parallel search to RecipeSearch.

rounded category boxes, redesigned add recipe buttons in mealplan, display categories in recipeview, improved GUI