This Commit Does Following:
- Fixes Heidemann API doc to match his provided API
- Fixes naming of Heidemann API to be descriptive and consistent
- Replaces the Usages of `href` with `routerLink` for a nicer SPA feeling
- Adds a Warn/Error/Abort style which can be used on `button` with the respective classes: `warn`, `error` and `abort`
- Adds a `shadowless` class which can be used on FAB `button` to disable its shadow
- Sets the default form style to be `outline`
- Fixes the Main Layout to include a `<main>` and have proper header and site structure
- Fixes `AuthService#logoff` to work
- Fixes `AuthService` to write the API token to the API client
