Add option to delete original item when dragged to another sheet

[jalensailin]

This PR introduces a feature that allows you to delete the original item when dragging items between sheets (by holding the Alt key when dropping). This mimics giving a player an item and saves time by not having to manually delete afterwards.

Steps to test:

1. Create two actors and give them each some items.
2. Open both actor sheets and drag items between the two.
3. Note, items are duplicated onto the receiving actor but still exists on the original actor too.
4. Drag items between the two sheets, this time holding down the Alt key.
5. Note, item is created on the receiving actor and deleted from the host actor.