[front-end, build] enable es6 support
[front-end] switch most code to es6 standard
[front-end] use ES6 classes
[karma, unit-test] fix unit-tests (load es6 polyfill in karma)
[front-end] rename browser-polyfill.js to es6-polyfill.js
[front-end] more es6 code
[front-end] enable JS sourcemaps support for compiled es6 code
Merge branch 'es6' into develop
[front-end, build] add widgets support for js source-maps
[unit-test, build] unit-tests support es6
[protractor] remove commented SAUSE_USER and SAUCE_ACCESS_KEY
Merge branch 'es6' into develop