Added invert mouse option.

Forms/ModelForm.cs

@@ -44,6 +44,7 @@ namespace CodeWalker.Forms
         int MouseY;
         System.Drawing.Point MouseDownPoint;
         System.Drawing.Point MouseLastPoint;
+        bool MouseInvert = Settings.Default.MouseInvert;
 
 
 
@@ -1051,6 +1052,11 @@ namespace CodeWalker.Forms
             int dx = e.X - MouseX;
             int dy = e.Y - MouseY;
 
+            if (MouseInvert)
+            {
+                dy = -dy;
+            }
+
             if (MouseLButtonDown)
             {
                 camera.MouseRotate(dx, dy);