Add support for SVG image tag

A support for SVG image tag. 

This is used in : https://github.com/lhausermann/the-graph/commit/7f8af669de55ced79b8a4e1420f04281a21fcc82

Note: This is not enough to be able to load an external SVG|PNG|JPG
image file. The main issue is we can not create valid JS to have
a property name "xlink:href". As today, we should use it using
a container object (say 'g') and set the image tag using
a dangerouslysetinnerhtml