Ask for samba password only if returned directory is NULL and errno is set to EACCES. https://bugzilla.gnome.org/show_bug.cgi?id=694150
Add class PpSamba which contains asynchronous function for searching for samba-shared printers. It can search for printers on local network or on a specific host if needed. https://bugzilla.gnome.org/show_bug.cgi?id=683229