Add SVG renderer

[gwatts]

SVG is probably the best way to handle high DPI devices instead of using canvas. Add it as a third renderer and use it in preference to VML/canvas where supported.

[aadrian]

+1 but maybe just as a second (or first :) ) option, since there are already libraries that handle VML on the fly: http://stackoverflow.com/questions/18201459/convert-svg-code-to-vml-code