Gradient fix

Added rendering of gradientTransform, fixed gradient position ( not working since big commit of svg import ) fixed use of xlink:href in gradients, stop opacity 0% was omitted. Fixed toSVG for gradients.
Added gradients for stroke property.

Related to issue #1597
Yes something like that, i had to use this mapping method, because otherwise i should use "getElementById" that we already stated is not compatible with ie9 from a xml document.