svgext svg/Shape extensions should be merged into svg/Shape

[cjolif]

We have now created first class versions of the shapes for both SVG and Canvas there is no more reason to extract additional SVG APIs to an extension module.
Also this is relatively limited LOC so should not put too much weight on the svg/Shape file size.
This will ease the use of those extensions without requiring to load other modules (in particular when building a component that can't necessarily rely on the module being loaded)