Set lower limit for object scale to 0x

Dealing with objects at a much smaller scale is fairly difficult. Some
other aspects of MPS would need to be tweaked to accomodate for this
change.

For now, the lower limit is set to 0x as per issue #44.

src/MeidoPhotoStudio.Plugin/DragPoint/DragPointGeneral.cs

@@ -197,7 +197,7 @@ namespace MeidoPhotoStudio.Plugin
             {
                 scaling = true;
                 float scale = currentScale + (mouseDelta.y / 200f * ScaleFactor);
-                if (scale < 0.1f) scale = 0.1f;
+                if (scale < 0f) scale = 0f;
                 MyObject.localScale = new Vector3(scale, scale, scale);
                 OnScale();
             }