* Detect libglib2.0-dev via pkgconfig
* Do not assume config files under ~/.config/ by hardcoding;
  should consider XDG standards.
* Do not hardcode tmp files under /tmp/.
  Should use library functions.
* The "Save As" function should set default file extension
  to "pgn" format.
* "Settings" page is not i18n-ed at all. We need to fix that
  problem.
