We need to add the ability to automatically move replicas to new brokers for a Kafka cluster scale up and remove replicas from soon to be decommissioned brokers.

Cruise control has the add brokers endpoint to allow rebalancing replicas off current cluster brokers to a number of newly added (empty) ones. It also has the decommission brokers endpoint to allow moving all replicas off a set of brokers so that they can be removed.

We should add the functionality to the KafkaRebalance to load new broker and decommission un-needed ones.