title: KSQL Streams and Tables does not persists data
body: <p>I create one kafka topic and i created a KSQL stream on this topic and i create a table on the stream to do aggregation,
  after restarting KSQL Server and Kafka, all KSQL Streams and tables gone !
  is there any way to configure KSQL Server to keep the streams and tables on the desk. 
  does it store the data on RAM only?</p>