Added support for session status decision
Worst plugin's result setted to UNSTABLE
Deleted unused imports
Changed filepath to XML file
Refactored code, added support of EnvVar in file path
Merge remote-tracking branch 'griddynamics/master'

Conflicts:
	src/main/resources/com/griddynamics/jagger/jenkins/plugin/JaggerComparisonPlugin/config.jelly
Merge pull request #9 from nmusienko/master

Some updates for support session status decision