feature request : adjusting masks to follow geometrig transformations

[pierrelabreche]

Consider a transformation with an associated mask created using the paint brush. When this transformation is moved to a new location in the tree, a revised mask could be computed to follow the geometric transformation at the new location.

For example, this feature would facilitate moving up or down over warp, and leveling. Of course, for non-intersecting image areas, a mask would have to be tweaked manually.