Polygons and polylines

Changed the way to handle polygon and polylines.
Before the FromElement function created the polygon / polyline skipping the parameter offset.
Now the offset is skipped just if the shape is inside a pathgroup.
Otherwise it gets calculated at first render cycle ( only way to know if the shape is inside the group or not, during init is or fromElement method is not possible ).

Also Top and Left get calculated , before not.
This makes possible handling of gradients and importing SVGs without grouping ( before if you imported polygon without grouping the bounding box was away from the shape ).