Reform data structure

Add class VmManager, SwcManager, RpcManager and ArpManager
vm_id generation

Use queue to generate unique vm_id for each VM.
Merge pull request #83 from powerist/failover

Code refinement
add arp test scripts from Pingkai, with modifications and fixes
Merge pull request #84 from changbl/working

add arp test scripts from Pingkai, with modifications and fixes
New failover

Add ZkManager to help manage zookeeper operation
Merge pull request #85 from powerist/failover

New failover
parallelize arp scripts to speedup
Merge pull request #86 from changbl/working

parallelize arp scripts to speedup
Gateway high availability

The controller installs two copies of the same flow entry
on (master gateway, backup gateway).
Merge pull request #87 from powerist/failover

Gateway high availability
Fix ARP eval scripts

(1) Timeout calculation

(2) ping.log text processing

(3) Speedup via more parallelizatoin
Merge pull request #89 from changbl/working

Fix ARP eval scripts