Remove scaling from perspective correction

Scaling is applied at the end of all geometric transformations, so it
would be more appropriate outside of the perspective correction tool.
Such an implementation would also work better with the auto-fit feature.

rtgui/paramsedited.h

@@ -407,7 +407,6 @@ struct PerspectiveParamsEdited {
     bool camera_yaw;
     bool projection_pitch;
     bool projection_rotate;
-    bool projection_scale;
     bool projection_shift_horiz;
     bool projection_shift_vert;
     bool projection_yaw;