If the execute loop of the scheduler class is not suitable for
a project, this method allows to retrieve the next action, that is,
the action with the lowest order number in the queue.
Since the LayeredMap class can only store integers,
but most games need some kind of objects to keep track
of item data, this class was introduced to create the
association from integers (map data) to some sort of
game-defined item data.
If you need a custom color map for your tile sheet, you can subclass
the GraphicsTilePainter and supply your color map through this
method. make sure to call this before you call stTileSheet()