transfer (file): use native file chooser on desktop: native file chooser is nicer and often more powerful than Kivy FileChooser. Kivy FileChooser is still activable with an option, for platforms where native file chooser is not easy/possible to use. Kivy FileChooser is used on Android. downloads_dir is now used as starting path on Android.

[DEFAULT]
bridge = pb
log_level = debug
log_fmt = #[%%(levelname)s][%%(name)s] %%(message)s

[cagou]
log_level = debug
log_fmt = [%%(levelname)s][%%(name)s] %%(message)s