…grid size

WebKit#52

Refactor the spiral iterator into a separate class. Keep calling its next() method
to get the coordinates ofthe next cell. When its isDone() returns true create a
new iterator and make the tiles of upper layers have less lightness than the ones
on the lower layers.

Add a new class for the roundedRect tile called "Tile". This class can handle the
location, size and animation of the Tile.