Shuffler Box

Added

• Swap hands to give the last block back. A building session always ended with one block in your hand that the box drew and you never placed, and the only way to return it was to put the box down, open it and drop the block in. Now swapping hands does it: the block goes back into the box and the box comes out into your main hand, ready to be put away. Only ever the block the box handed you -- cobblestone you mined yourself swaps across untouched, even when the box stocks cobblestone -- and anything that will not fit rides to your off hand as it always would.