change behaviour of chain quests (scrolls to owner only) - fixes https://github.com/HabitRPG/habitrpg/issues/2715

Goes along with another PR that I'm about to make.

- allows quests to provide certain rewards (e.g., quest scrolls) to the quest owner only ('itemsForOwner', which can be used instead of or as well as 'items')

- adjusts vice2, vice3, atom2, atom3 so that they can not be purchased (canBuy:false)