Kafka-utils

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* Add storage option for a few kafka_consumer_manager subcommands
* Change default offset storage from zookeeper to kafka
* Autodetecting the number of partitions for the __commit_offsets topic

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* Fix integration tests

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* Refactor kafka-cluster-manager to support multiple balancer classes and metrics
* Add PartitionMeasurer class and --partition-measurer option for providing user partition metrics
* Add --genetic-balancer option to kafka-cluster-manager to make use of the genetic balancer
* Change kafka-cluster-manager stats command output to include user partition metrics
* Add --show-stats option to kafka-cluster-manager rebalance

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* Fetch group topics only from a single __consumer_offsets partition

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* Add offline partitions check for kafka-check

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* Fix set_replication_factor command plan generation