Important fixes (BREAKING)

• Breaking change: Route for opening a mystery item box now returns the item obtained as stored in Content's items.gear.flat, instead of the user's entire items.gear.owned.
• Fix: Checklists no longer overwrite prior items with new item's data
• Fix: "Tag list in tasks starts collapsed" option works as written, instead of starting tag list expanded when checked
• Fix: Sanitize tasks created/edited by v2 routes to prevent broken tasks
• Fix: Challenge tasks no longer legal targets of spells in v2
• Fix: Don't allow direct modification of task.value in v2
• Fix: Tasks are no longer created with tags corresponding to inactive filters
• Fix: Tags can be removed from tasks
• Fix: Don't use Angular $watch to monitor drops and Mystery Items
• Fix: Mystery item icons display correctly in notifications