Made recurringBox contain a boolean instead of a yes/no string, in order to bind it together with the recurring attribute

Set the comboboxes to default values. Added comment to setExpenses, because amount textfield is stored with comma, which is not a double

Added comments to explain expense attributes. Added todo for setExpense - changes are still saved even if the cancel button is clicked when editing an expense

Instantiate observable list in initialize(). Made method baseline for filehandling method to save changes in expenses

Made amount attribute to DoubleProperty. Binded amount textfield in AddExpenseController to the expense amount property

Made handelAddBtn and handleEditBtn essentially be the same method, and differentitated them with enums

Reconfigured pom file for updated javafx version. Redesigned addExpense, Expenses and MainMenu, which is reflected in the fxml files

Implemented methods in AddExpense and Expenses such that information flow occurs between the two classes

Created new Expense Controller, renamed old Expense Controller to ExpensesController, and created two other new controller classes for testing

Created class for FileHandling GeneralBudget objects

See merge request !22