Major changes

* I have created an intermediary script `spideroak` that actual
  handles the start of the SpiderOak process as well as applying
  the user settings. A PID file is also created, which allows
  systemd to track the SpiderOak process.

  I did this because it means now that users should be able to
  configure SpiderOak individually instead of having a system-wide
  configuration file.
* The service file is almost unchanged, execpt for the fact that it
  calls the `spideroak` script instead of the SpiderOak binary.
  Furthermore, the home-directory of the user ("%i") is passed to
  the script.

More is being worked on, but I need to test this a bit more...