+ AggregatorProviderWithSettings
+ TimeUnits
+ MetricDescriptions contains aggregators with settings
+ add NONE to TimeUtils
+ change aggregationInterval type to int - due to IntervalSizeProvider interface
+ move all calculation of aggergation interval size to StatisticGenerator
+ little renaming inside methods
+ remove AggregatorProvider wrapper - use BiMap.
+ MetricAggregatorSettings as public class
Merge pull request #481 from amikryukov/aggregators-with-set

JFG-699, JFG-700 add Settings to Aggregators