now populating clusterId and serviceId when saving to ZK
now can register more than a single callback
updated docs with example of registering another callback to RotatingMetricRegistryManager
fixed NPE when dealing with older format data
added support for multiple callback classes
fixed input type for setDataNodeCount from int to Integer; added lastUpdatedTimestamp field
added service label to header of each section
adding service name to header of each section
cleaned up UI
using camelcase
using camelcase
using camelcase
removed JsonIgnoreProperties annotation:  did not seem effective
reduced noise on some logs; catching unrecognized field exception
Merge branch 'develop'