Improved install script

- Indent using tabs. Meanwhile using tabs seems to be best practice. See:
  https://projects.archlinux.org/pacman.git/tree/proto/proto.install
- Use sudo -u instead of su -.
- Add a hint for using backup rake tasks.
- Removed a oneliner funktion.
Patch service file in prepare()
Fixed tons of broken symlinks

- Readded secret as I now understand why it did not work in the first
  place :)
- Changed logdir owner to gitlab