XDG basedir location for data/cache/configuration files

This library implements the xdg-basedir specification. It helps to define standard locations for configuration, cache and data files in the user directory and on the system. It is a straightforward implementation on UNIX platforms and try to apply consistent policies with regard to Windows directories. It is inspired by the Haskell implementation of this specification, and it follows the same choices for Windows directories. See he xdg-basedir specification and the Haskell implementation.