Address review of initial RebalanceController work

- Removed 'timeout' option for rebalancing since always setting timeouts
  to infintie (Long.MAX_VALUE) is the recommended practice.

- Cleaned up some TODOs and added some javadoc in response to code
  review from Lei
Fix invalid metadata rate calculation

Fixed the calculation of invalid metadata rate in RebalanceUtils. Also added more/different pretty printing of a rebalance plan.
Minor TODO and copyright cleanup.
Fix some bugs I introduced and added more TODOs

Fixed overflow introduced in AdminClient.waitForCompletion by passing in
Long.MAX_VALUE for duration.

Verify cluster store definition in StoreRoutingPlan. This requires
working around existing problems with how system stores are handled (the
store definition is hard-coded for two zones). Left some TODOs about
testing and fixing all of this.

Added TODOs about currentCluster vs interimCluster. Need to tweak
interface to RebalanceController and RebalancePlan to be consistent with
recommended usage (i.e., deploying interimCluster before starting
rebalance).

Minor tweaks to tests based on above changes.