Move Selected Items In Design Mode

User must have the ability to place items in Design Mode by dragging the selected item around. This should avoid using transform attributes where possible:
- move affects x,y for rects, images, uses
- move affects cx,cy for circles/ellipses
- move should affect the first absolute move point (all other path commands should be made relative upon the first drag)
- move should affect all points in line, polyline, polygon

NOTE: Moves/drags should ensure that the element keeps its parent (i.e. its containing group).