[configuration] Use XDG (freedesktop) locations
@bilboed
Submitted by Edward Hervey Assigned to Brandon Lewis @brandon_lewis
Description
PiTiVi needs to remember the various configurations (window position, which mode, default and user presets, ...).
I'm still hesitating between having a .pitivi configuration file/directory and using gconf keys.
GConf is the way to go for gnome apps, but using file/directory would allow PiTiVi to be used by non-gnome users too.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=335547