MapViewport handling of AffineTransform and ScreenArea

MapViewport is not doing a good job of helping client code mange the relationship between the "Bounds" representing the foot print of the map on the earth; and the screen area Rectangle used to display the map on the screen. The conversion between the two amounts to an AffineTransform.

JMapPane code use an additional AffineTransform to handle rotation and zooming. I would like to roll this code into MapViewport in order to make JMapPane easier for user to understand; and to collect all out transform stuff into once class for testing and reuse.