added test durations: 10,30,50 min; <skipTests>true</skipTests>
Test Duration: change combo-box to text-field
Test Duration: add validation
Text field value: validation on GUI
Text field value: validation on GUI, change logo
Test duration should be more than ZERO, build is considered as Result.NOT_BUILT
doCheckTestDuration
Aborting build if input values are invalid
Clean BlazemeterAPI
update version from 1.424 to 1.576
JEN-22: fix exception with empty testDuration
JEN-22: skip treshold asserting if values equal 0
checkUrl="'descriptorByName/hudson.plugins.blazemeter.PerformancePublisher/