Do not override $sig_stop to be -QUIT
The init scripts that come with Linux versions of Plex were used as
inspiration for the FreeBSD rc script. They use SIGQUIT when shutting
down Plex, but on FreeBSD this causes a core dump. SIGTERM seems to work
Add capability to override default maximum number of plugin processes in
rc.conf. This mirrors the capability found on Linux and is only required
in rare circumstances when the user has installed 3rd party Plex agents.