Enable rendering while loading only the required part of geometries, like tiles in images

The current design of geometries in j2d-renderer (Polyline as linked list of LineString) lead naturally to the separation of a single geometry in many parts, an idea similar to Tiles in RenderedImage. Together with the streaming approach in the new FeatureSource architecture, it should allow the loading of only required parts. For example if a huge polygon represent the whole North America but the user zoom only on the West coast, coordinate points for the rest of America doesn't need to be loaded even if they are part of the same geometry.

j2d-renderer should be updated to take advantage of streaming behavior in FeatureSource.