MAGETWO-72076: Update benchmark.jmx and README files in Performance Toolkit, add performance analytics script

- Synchronize benchmark_2015.jmx and scenario compiled from fragments

Author: Andrei Malets

setup/performance-toolkit/benchmark_2015.jmx

@@ -1,10 +1,4 @@
 <?xml version="1.0"?>
-<!--
-/**
- * Copyright © Magento, Inc. All rights reserved.
- * See COPYING.txt for license details.
- */
--->
 <jmeterTestPlan version="1.2" properties="2.8" jmeter="2.13 r1665067">
   <hashTree>
     <TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="Performance Toolkit" enabled="true">