Add usage scenario for RabbitMQ Filter and Tee filter in Configuration Guide

Please document a usage scenario - where a Tee filter and RabbitMQ filter both are used by a service. Please explaing the usage scenario and then provide example configuration for the service, filters and routers.

Here is what flow of queries should be

                         |---> RabbitMQ Server

  Client ---> MaxScale---|

                         |---> MariaDB database Server

Use case configuration of the Tee-filter should be such that only Insert, Update and Delete queries are duplicated to RabbitMQ Server, where as all the queries will be sent to the backend database.