Add support for macOS "Move item here" shortcut

[laurent45654]

In macOS, if I copy a file in Finder, and paste it somewhere else using Cmd+Opt+V, it's actually going to move (cut) the file. That works in most app in macOS but not in XnView.

That makes it annoying to move files in and out of XnView - for example I may download an image, which I want to put in the XnView folder I'm working on, and I have to first copy it, paste it into XnView, then go back to Finder, and delete it. A way to cut files would be very convenient and will improve the integration with macOS.

The menu item in macOS is called "Move item here":