Adds a dependency on PackageKit...
In better news:
- Default to PDF when saving in all cases.
- Always show file format options and use a combo box to fit better into
dialog.
- Detect HP scanners and install drivers using PackageKit if found.
- If SANE detects no scanners but we see USB IDs of Brother, Epson or
Samsung scanners then prompt the user to go to their website to install
drivers.
- Use GUsb instead of GUdev.
- Fix error dialogs not showing.