Migrate to WebPack, add M3

ToDo @fefrei:

• hook up offline plugin to UI
• confirm service worker can be uninstalled in case of malfunction
• write out version.txt in a way that is compatible to the offline plugin

ToDo @fkosmale:

• move dependency injection information to defining file
• fix flash of unstyled content, confirm ng-cloak is operational
• check status of Firefox LTS display bug
• update documentation