Hstore support in Postgresql-connector

Hstore data types in postgresql are either ignored by postgresql connector which is the default property of the connector , however if the consumer wants it then the consumer can set "include.unknown.datatypes" : true" which results into hstore representation in the form of binary text.Postgresql connector should be able to support hstore types and send as part of message along with other fields .
With this feature , users will be able to set the property `hstore.handling.mode` to map || json , depending on which representation they want in Kafka Connect . By default its set to map