Script modifications to make things easier to start/stop

1. The scripts will run as the user who owns the file. For example,
   if the file is owned by "www-data" it will run as that user
   if executed as root.
2. The script has init.d headers. On Ubuntu/Debian, it one can
    link to the file in /etc/init.d and then run:
        "update-rc.d install <NAME> defaults"
    This makes it really easy to ensure that seafiles starts and
    stops. Tested on Ubuntu 12.04 and Debian (Rasberry Pi)