- the _get_default() method is now async
- the PackageKit module will return NULL in case PackageKit is not
available in the session bus
- the dummy module doesn't exist anymore
- the dialog won't display the online button in case there's no module
available
This commit adjusts the app chooser code to GTK+ coding style:
- line up prototypes
- remove some excess {}
- remove tabs and trailing whitespace
- add docs