FIX: grabber moving distance is too small

When dragging in 3D scene, the grabber's moving distance is less than the mouse's moving distance

Change-Id: I7b766a73b7e862fb6304531c75502b09702eb128
(cherry picked from commit 82ebcd38e50c63bcfe5863dd4ff87b93df5a771e)

src/slic3r/GUI/Gizmos/GLGizmoScale.hpp

@@ -19,6 +19,8 @@ class GLGizmoScale3D : public GLGizmoBase
     {
         Vec3d scale;
         Vec3d drag_position;
+        Vec3d plane_center;  // keep the relative center position for scale in the bottom plane
+        Vec3d plane_nromal;  // keep the bottom plane 
         BoundingBoxf3 box;
         Vec3d pivots[6];
         bool ctrl_down;