Option to output in JSON format

[jakub014]

Current output is only comma-separated. Change it to JSON. Alternatively, when output is Kafka always use JSON format to reuse the topic from KafkaQuery

[jakub014]

Flink 1.13 Row class will contain very promising functionality to simplify implementing this feature. Therefore this is postponed until then.

[jakub014]

Implemented, this feature can be accessed through the command -o kafkaJson=<topic_name>