Merge pull request #163 from metacret/master

COUNTER is changed to GAUGE and zk_num_alive_connections is added
- manual-restart configuration is added in UI and IntConfigs

If this is true, on any configuration change, exhibitor does not restart zookeeper

- In MonitorRunningInstance, when exhibitor should restart zookeeper such as configuration change or server list change, it just schedule restarting zookeeper. When the current rolling host name is itself(implemented on ConfigManager.isRollingMe) and restarting zookeeper is scheduled, exhibitor actually restart the zookeeper. When manual-restart is true, restarting the zookeeper wouldn't be scheduled