adds setting screen

src/service/interface/dbusservice.vala

@@ -13,9 +13,6 @@ namespace DBusService {
 		[DBus (name = "Username")]
 		public abstract string username { owned get; set; }
 
-		[DBus (name = "CredentialItem")]
-		public abstract GLib.ObjectPath credential_item { owned get; set; }
-
 		[DBus (name = "SetServer")]
 		public abstract void set_server(string url, string user) throws DBusError, IOError;