Improved benchmark report formatting
Improved benchmark report formatting

- Results are displayed more compactly in the report
- Only nodes with significant performance changes are displayed in execution summary comparisons

Change-Id: I51fe1f71760ba451b23d3d0ec31358c848e54976
Reviewed-on: http://gerrit.sjc.cloudera.com:8080/3979
Reviewed-by: Taras Bobrovytsky <72e4a6fc4c5ef23f318dc209e8402725249a5676@cloudera.com>
Tested-by: jenkins

ImpalaToGo/ImpalaToGo,placrosse/ImpalaToGo,placrosse/ImpalaToGo,ImpalaToGo/ImpalaToGo,AtScaleInc/Impala,andybab/Impala,andybab/Impala,andybab/Impala,andybab/Impala,ImpalaToGo/ImpalaToGo,gistic/PublicSpatialImpala,AtScaleInc/Impala,AtScaleInc/Impala,gistic/PublicSpatialImpala,AtScaleInc/Impala,andybab/Impala,AtScaleInc/Impala,ImpalaToGo/ImpalaToGo,gistic/PublicSpatialImpala,placrosse/ImpalaToGo,gistic/PublicSpatialImpala,ImpalaToGo/ImpalaToGo,placrosse/ImpalaToGo,gistic/PublicSpatialImpala,ImpalaToGo/ImpalaToGo,AtScaleInc/Impala,gistic/PublicSpatialImpala,placrosse/ImpalaToGo,andybab/Impala,placrosse/ImpalaToGo