+ fetch plot data with batches for Throughput, Latency, TimeLatencyPercentile, CustomMetrics
   monitoring still the same
+ CashedThreadPool instead of FixedThreadPool
+ avoid throwable.printStackTrace() and System.err/
+ StandardMetricPlotFetcher for throughput, latency, latencyPercentile
+ dummy code cleaning
- remove all PlotDataProviders except MonitoringDataProvider
Merge pull request #436 from amikryukov/webui-performance-plots

JFG-609 fetch plot data with batches