[FIX] (Tooltip Intermediate Scenes) The tooltip would not show in intermediate scene zones in Area and Line marks. Now the tooltip is redirected to the main scene.
[PERF] (protovis Area Line) Area and Line marks with interaction enabled would render much slower that when non-interactive. An overlay of fully-segmented paths existed solely to detect events for each scene/instance.
By implementing scene/instance index redirection, the events overlay is not needed anymore.