Confirm inventory deletion upon certain circumstances

[Assembling-Kings]

• Shows a confirmation dialog when the user tries to lower an inventory item's quantity to 0.
  • The same confirmation is also shown when lowering an item's damage state past 'Major Damage'
• Fixes a bug when changing an item damage state inside a container with scrollbars. Previously it would scroll to the top instead of retaining the scroll position.

Note:

• Implements #141