lnrpc+lncli: add command to print macaroon

cmd/lncli/main.go

@@ -304,6 +304,7 @@ func main() {
 		listMacaroonIDsCommand,
 		deleteMacaroonIDCommand,
 		listPermissionsCommand,
+		printMacaroonCommand,
 		trackPaymentCommand,
 		versionCommand,
 	}