[front-end, bugfix] fix page deletion
[front-end, docs] Write docs for most widgetApi stuff.

Use prototype-based methods in APIProvider, APIUser, EventPublisher
[front-end] move SCEditor bug-fix hack out of controller
[front-end] add the button of a new page addition
[front-end] add  window for a new page addition
[front-end] implement new page addition
[front-end] fix json-editor for android
[front-end] fix-up on previous commit
[front-end, build] generated templates.js is now a requirejs module
[front-end] fix front-end in production mode
[gulp] refactor - use dot notation for property
[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] various index.html refactorings (e.g. /> to > replacement)
[front-end] more es6 code
[front-end] enable JS sourcemaps support for compiled es6 code
[gulp] fix comment