Free placement of cards on board

[Meepox]

Let storyteller place no limit of cards on board.

Let people stack cards over each other.

When selected and placed, card is put on top of stack (in terms of layer)

[ktorng]

drag into (x, y) coordinates on the board instead of having 8 preset slots

also need to store info on a card the storyteller is currently dragging around, so that other players can see it in real time