Integrating Kafka partitioning scheme with Voldemort cluster.xml

- Rename KafkaConsumerDefinition to KafkaTopicDefinition as it will be used by both client and server
- Read from cluster.xml to initialize the VeniceStore
- Add consistent partition, serializing classes for Kafka to use
- Adding KafkaRoutedStore object for producing objects into Kafka
So the way I planned on having this done was that the OperationType parameter would be the differentiation (which is resolved right here).

If the operation type is a partial put, then we would mutate the Venice key into a Kafka key here. (Prefixing the "1_subschema_")

I'll add a TODO node so that when partial puts are implemented, the change can be made here.