Add easier headless configuration.

This will allow setting up a remote with copy&paste of values to a headless machine. It will allow copy+pasting a token into the configuration.

This requires rclone to be on a machine with a proper browser. Custom client id and secrets are supported.

To test token generation, use `rclone auth "fs type"`.

rclone.go

@@ -224,6 +224,18 @@ var Commands = []Command{
 		},
 		NoStats: true,
 	},
+	{
+		Name: "authorize",
+		Help: `
+        Remote authorization.`,
+		Run: func(fdst, fsrc fs.Fs) error {
+			fs.Authorize()
+			return nil
+		},
+		NoStats: true,
+		MinArgs: 1,
+		MaxArgs: 3,
+	},
 	{
 		Name: "help",
 		Help: `