Client/Tools/FreeBSDInit: rework the whole tool

The new FreeBSDInit tool uses the service and sysrc tools
to manage the FreeBSD rc.d services. There are no hardcoded
paths to /usr/local/etc/rc.d/ anymore and the service tool
handles rc.d scripts in /etc/rc.d/ as well.

Additional to that, the new tool also gathers information
about extra services that are enabled (using service -e)
and can enable new services with sysrc. This is a frontend
for /etc/rc.conf and therefore changes that file.