#6 User configuration file location

[Federico Brega]

User configuration is stored in a directory in the user's home folder.
XDG base directory specification (http://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html) states that the application should look at
$XDG_CONFIG_HOME and fall-back to $HOME/.config instead it currently writes in $HOME.
The old configuration file should be moved to the new location.