Fix #9 new challange tasks in last position (#13)
Fix #9 new challange tasks in last position (#13)

- New `ChallengeTask` items should be put in the last position (fix #9)
iafb/gra4,MCLD/greatreadingadventure,haraldnagel/greatreadingadventure,MCLD/gra4,haraldnagel/greatreadingadventure,MCLD/greatreadingadventure,justinmeiners/gra4,haraldnagel/gra4,haraldnagel/greatreadingadventure,MCLD/greatreadingadventure,MCLD/gra4,justinmeiners/gra4,MCLD/greatreadingadventure,haraldnagel/greatreadingadventure,MCLD/greatreadingadventure,iafb/gra4,haraldnagel/gra4