Unseen Tiles pop-up window can't be moved -- could do it in V1

[b birney]

In V1, you could click on Unseen Tiles, and then move the pop-up window to the side, so that you could see most or all of the board in play. That way, you simultaneously see both the active board and the remaining tiles, which can help with strategy.
Please keep it working like that in V2.