Dealing with files with spaces in filename

[karlch]

Although these are loaded properly, there are still various methods that simply rely on string.split() and continue from there (e.g. undelete). This fails for files with a space in the filename.

We should provide some central way to escape spaces all over vimiv, possibly using some existing framework or Gtk, GLib, ... internal.

[karlch]

This should have been solved with commit 1e15ede for command calling. Closing as I have not run into any issues since then and global escaping does not seem necessary.