Viewer Mode - Crop improvements

[daflow]

Please consider the following improvements to the Crop functionality:

1) Remember crop aspect ratio so that on next start the chosen ratio is still selected.

2) Increase width of grab area for resizing. It is so small that I often rotate the selection accidentally instead of resizing the selection.

3) Undo does not work for changes to the crop selection. This would be extremely helpful in case one accidentally rotated the selection instead of resizing it.

Thanks!

- Daflow

P.S. Thanks for XnViewMP, it's great!
P.P.S. All observations made on Win10 64bit with XnViewMP Version 0.96.4 64bits (Jun 30 2020)