Add mechanism for injecting render-specific props #640
Description
e.g.
<Rect renderMetadata={{
// apply css id/class when using SVG Renderer
id: 'the_rect',
class: 'drawable
}} >
{{ message }}
e.g.
<Rect renderMetadata={{
// apply css id/class when using SVG Renderer
id: 'the_rect',
class: 'drawable
}} >