Save SVG meta data for consistent rendering

[TeemuSuoranta]

The SVG support is great but it could be a little more robust. Current implementation will not save any meta data for SVGs so when they are used as images they have no width/height attributes that may lead to inconsistent renedering on older browsers.

Some SVG plugins like safe-svg do save the meta data but implementation is probably a bit hacky https://github.com/darylldoyle/safe-svg/blob/master/safe-svg.php#L398

Not super critical but if there are more people with this issue, they might consider using external SVG plugin.