Also add a "rating" and "timePlayed" variable to GameData. Some cleanup
in GameData and FolderData. Added sorting functions for rating and
timesPlayed to FolderData. Testing and UI support still tbd.
Folders should now be sorted alphabetically.
Will now fall back to a system font if LinLibertine.ttf is not found.
Added a Menu button.
Began working on a simple menu.