+Also: if new live game starts in background, "new game" notify OK but not first move (not too serious however)
+
+For Teleport, Chakart and Hamilton at least: a piece should be attached to mouse cursor,
+waiting for a click dropping it somewhere. In BaseGame: find the appropriate place to call eg. Board::setHoverPiece(),
+which should be in effect when hovering over position only (#gamePosition), and cancelled when receiving the
+message stopHover() for example.