base64 encoded svg support needed

[ngaurav]

<svg> tag is supported but when svg image is present inside img tag it fails to get rendered.
For example <img src='data:image/svg+xml;base64,...../> will throw an error.
I can see that both <svg> tag and <img> tag are a subclass of ReplacedElement. But current implementation ignores the meta data (image/svg+xml) inside <img> tag.