Correct scale synchronization when drag/drop editing SheetPlacement

[9swampy]

Drag drop works, but only for small movements. If you drag too far the mouse gets ahead of the part being dragged and the drag terminates. Current work around is to make multiple small movements but it would be better if the drag kept in sync with the mouse movement.

[Lukrative525]

This is fixed in my "development" branch on my fork if you're interested.

Edit: see 06daa3d.