Add Swapping toggle button to StoryItem options

[birbilis]

Could have a separate swapping property for StoryItems to allow quick swapping of items:

• by moving onto each other
• by clicking in order (could remember the last one clicked [maybe could even switch parents that way])

non-moveable items that are swappable could allow dragging them and if not dropped upon another swapping item they could return back to their place (maybe an exception could be if they're dropped on a non-swappable items with a magnet, they could stay snapped there)