Sundry clean up in voldemort/utils

UpdateClusterUtils
- added new utils class
- moved all cluster & node manipulation methods to this class. (E.g.,
  methods that tweak partition IDs on a node, and methods that copy
  all nodes in a cluster, etc.)

Cluster
- replaced implementation of .cloneCluster() with another helper
  method's implementation.

PartitionBalanceUtils
- new utils class
- moved all helper methods that analyze cluster/storedef to this class

RebalanceUtils
- many helpers moved out of here to more other, new util classes

ClusterUtils  & NodeUtils
- found new homes for all helper methods. Will drop these files in
  next commit.

Dropped ClusterUtils and NodeUtils

Add pointer to proxy-put-metadata-listener branch.