Support SSL communication in Kafka IO plugin of Apex-PDP

As a ONAP developer, I would like to enhance the current Kafka IO plugin in Apex-PDP to support SSL based communication between Kafka cluster and Apex-PDP engine.

Current implementation of the plugin is here - https://github.com/onap/policy-apex-pdp/tree/master/plugins/plugins-event/plugins-event-carrier/plugins-event-carrier-kafka

Current documentation for the plugin is here - https://docs.onap.org/projects/onap-policy-parent/en/guilin/apex/APEX-User-Manual.html#kafka-io