(WIP) Graphics - add ellipticalArc method

First pass at fixing #1443.
Created ellipticalArc method based on <a href="http://www.w3.org/TR/SVG/implnote.html#ArcImplementationNotes">w3c elliptical arc implementation notes</a>.

Added manual example based on <a href="http://www.w3.org/TR/SVG/paths.html#PathDataEllipticalArcCommands">this example in the path spec</a>.

Currently, VML/Canvas implementations are drawing arcs by point. May consider using cubic bezier approximations depending on performance.

- [ ] Add unit tests. 
- [ ] Cross browser/platform testing
- [ ] Perf testing.
- [ ] Update based on any feedback.