Introdcues a new update service.
Listens to service-worker updates and shows a snack-bar to inform about updates.
Provides a function to manually check for updates.
The service worker tries to be consistent in it's own version and
updates in the background.
Some manuall trigger will be required to update, which is either a
reload or the execution of the provded check function
with help from
@FinnStutzenstein
