Tutorial finished and tasks list added

Gameplay Update:

- The Tutorial is finished! It covers the different parts of the gameplay and runs 'til the end of the 15th wave. As the Campaign is not yet created, the successful finish of the tutorial is not yet unlocking the first real Campaign map, but that will also be done later.

- Started working on the Tasks List control. Currently, all the functionalities have been done, now I "just" need to add the contents of each tutorial step, but that takes some time because of the translations and calling the logics at the right place.

- Now the game displays different messages on the end game screen after loosing/winning the game.