Look into writing more modern JavaScript

[JeffreyDevloo]

Enhancement description

The front-end is currently written in an outdated JavaScript version (ES3). We should look into writing in ES6 and transpiler to port it back to ES3 or ES5. We could attempt an upgrade towards Aurelia (next version of Durandal) This way we can write code faster as we currently have to keep outdated stuff in mind and look into polyfilling multiple newer features ourselves