Known bugs:

- If you execute cut, then drag&drop files from another window, cut operation 
will be assumed.
- Callback for tree view widget is erratic - it usually doesn't work on Enter 
key and sometimes it is sufficient to press arrow up or down to enter a 
directory.
- In icon view, holding shift while clicking has the same effect as ctrl (i.e.
adds just the focused widget to selection, not the ones in between)