Change Repartioner to swap among nodes from all specified zones.

PartitionBalance
- Added comment about possible weakness of our utility method.

Repartitoiner.java
- Changed random shuffle implementation to swap among all nodes in
  specified zones.
- Left TODOs and 'dead code' implemntation of intra-zone swapping vs
  inter-zone swapping.
Add rebalance shuffle script
Fix location of example stores
Add cluster expansion script
Fix comments
Get rid of tee-ing the plan to a separate file

The rebalance planner writes the output to a file named
plan.out so this is not needed anymore.
Remove vold_home parameter from scripts

These scripts are being shipped as part of vold repo and so
no need for this extra parameter.
Copy plan outout to the final directory
Cleanup minor typos and comments
Expose max contiguous partitons option to script
Make repartitioner interface consistent + cleanup
More cleanup to repartitioner

Fix varible names, typos add comments
Rename new cluster script
Copy analysis file to output_dir