[NOBTS]add export image function in test report detail page.
Merge branch 'master' of https://github.com/nhnopensource/ngrinder.git

Conflicts:
	ngrinder-controller/src/main/webapp/WEB-INF/ftl/perftest/report.ftl
	ngrinder-controller/src/main/webapp/js/drawChart.js
Merge branch 'master' of https://github.com/nhnopensource/ngrinder.git