Support XDG Base Directory Specification

Configuration files and cookies are now stored in "$XDG_CONFIG_HOME/lgogdownloader"
if $XDG_CONFIG_HOME is not set it will use "$HOME/.config/lgogdownloader"

XML files are now stored in "$XDG_CACHE_HOME/lgogdownloader/xml"
if $XDG_CACHE_HOME is not set it will use "$HOME/.cache/lgogdownloader/xml"