Final commit

src/main/java/edu/ntnu/stud/TrainDeparture.java

src/main/java/edu/ntnu/stud/TrainDepartureRegister.java

src/main/java/edu/ntnu/stud/UserInterface.java

src/main/java/edu/ntnu/stud/ValidityManager.java

src/test/java/edu/ntnu/stud/TrainDepartureRegisterTest.java

src/test/java/edu/ntnu/stud/TrainDepartureTest.java

src/test/java/edu/ntnu/stud/ValidityManagerTest.java