DrawingContext.DrawImage() method not draws an SvgImage in some cases

[VladimirDrobyshev]

If target rectangle has non zero location and its size is not equal to SvgImage size the SvgImage is not dfrawing correctly.

SvgImage with size (20, 20)

1. not drawns:

        context.DrawImage(svgImage, new Rect(100, 100, 10, 10));

2. drawns correctly:

        context.DrawImage(svgImage, new Rect(0, 0, 10, 10));

3. drawns correctly:

        context.DrawImage(svgImage, new Rect(100, 100, 20, 20));

[wieslawsoltes]

Fixed by #228