Decorator - Support for newline and tab

Currently graylog decorator not supporting new line and tab, requesting to support this

please refer https://community.graylog.org/t/decorator-combine-to-field-values-with-newline/315

## Expected Behavior

In decorator, if you are combining two string, we need option to add new line also eg : Format String : ${Input_App_Name_01} \n ${Input_App_Name_02}

Should result like
Input_App_Name (Field)
oneday_profile (app one)
/base/test/parse//userprofile/oneday/profile (app two)

## Current Behavior

Currently we are getting result like

Input_App_Name (Field)
oneday_profile (app one) n /base/test/parse//userprofile/oneday/profile (app two)

## Possible Solution

## Steps to Reproduce (for bugs)

1. Select two filed from result example Input_App_Name_01 and Input_App_Name_03
2. create extractor Format String : ${Input_App_Name_01} \n ${Input_App_Name_02}
Target field : Input_App_Name
3.
4.

## Context

## Your Environment

* Graylog Version: 2.2
* Elasticsearch Version:
* MongoDB Version:
* Operating System:
* Browser version: