Support dragging SVG elements

[cybersmily]

Ability to applying the dndDraggable directive to SVG elements (rect, circle, etc.) so that a user can move SVG elements around the page.

Currently it doesn't seem like that dndDraggable works with SVG elements, even though Angular supports SVG components. I attempted add the directive to a rect element and it fails to handle the events for dragging. The dndDropzonen does work for dropping data to SVG elements.