shape-rendering attribute

[remiohead]

https://developer.mozilla.org/en-US/doc ... -rendering

I think this should be set to "crispEdges" for horizontal and vertical lines, rectangles, and Path2D shapes made up only of horizontal and vertical lines. The result looks considerably better for almost all JFreeCharts I have tested it with.

[david.gilbert]

I'm making this configurable for the next release. In some cases, I see strange results with "crispEdges" (gridlines disappear for example) but in other cases you are right that it looks sharper.