#99 Implement usual copy, cut and paste functionality

[linuxdirk]

I was shocked, as I learned, that there is no functionality to easy copy and paste (or cut and paste) files with the usual shortcuts (Ctrl+x for cut, Ctrl+c for copy, and Ctrl+v for paste). There seems also be no menu entry for doing so. I always have do drag and drop my files instead of simply use short cuts for doing so.