[docs] Update FreeBSD install scripts

- Add required protobuf-c package
- Remove version numbers so we don't need to keep them updated

scripts/freebsd_start.sh

@@ -0,0 +1,25 @@
+#!/bin/sh
+ 
+# PROVIDE: owntone
+# REQUIRE: avahi_daemon dbus
+ 
+# Add the following lines to /etc/rc.conf to enable `owntone':
+#
+# owntone_enable="YES"
+# owntone_flags="<set as needed>"
+ 
+. /etc/rc.subr
+ 
+name="owntone"
+rcvar=`set_rcvar`
+ 
+command="/usr/local/sbin/owntone"
+command_args="-P /var/run/owntone.pid"
+pidfile="/var/run/owntone.pid"
+required_files="/usr/local/etc/owntone.conf"
+ 
+# read configuration and set defaults
+load_rc_config "$name"
+: ${owntone_enable="NO"}
+ 
+run_rc_command "$1"