mask oval gradient tool with intermediate control points user interface

[pierrelabreche]

When creating an oval gradient mask with intermediate control points, concentric oval outlines are not displayed .
It would be convenient to visualize the concentric ovals and to enable modifying the location of control points directly by resizing inner ovals.

These capabilities are offered by the oval gradient transformation.

[jsachs]

As it turns out, I already implemented something similar for linear and oval gradients earlier today.