adding sickbeard_start function to init.freebsd

the changes in this pull request allowed me to do the following, all in working order:

    root@usenet:/usr/local/etc/rc.d # service sickbeard start
    Starting sickbeard.

    root@usenet:~ # service sickbeard status
    sickbeard is running as 53554

    root@usenet:~ # service sickbeard stop
    Stopping sickbeard
    Waiting for PIDS: 53554.
    Stopped

1. there was no start function in the init script so I added one. Previously, starting sickbeard via the script did nothing at all.
2. the shutdown script did not work, so I changed the http request to reflect the actual shutdown url.

my testing environment for this script is FreeBSD 10.0-STABLE. I'd be happy to work more on this script if it is needed.

Let me know if you have any questions.