Feature request: arbitrary commands on image filenames.

[o-jasper]

Running commands could be nice. For instance feh -A "mv %F ~/wherever, you can press 0 to move the file. But of course that could be anything. It could like open a text file kate ~%F.markdown or some such. Could allow specifying those both in the commandline and the ~/.config/ file. Of course preferably also attachable to key binding (#84)