Firewall: Proper allow to create REDIRECT rules.

Firewall: Proper allow to create REDIRECT rules.

This patch now proper allows to create rules for redirecting requests of a
given host, group or network(s) to a specified port or service to the
local IPFire system.

So it implements a very generic and easy to use feature to redirect
(for example all DNS, NTP, or whatever) requests to the a local running
instance and so to force usage of that local hosted service.

* The feature supports specifiying a single port and redirect the requests to another given one.
  ( For example requests to UDP 123 can be redirected to local UDP 1234
  if you run an NTP server on that port.)

* It also supports direct usage of services or even service groups.
  ( So you can create a service group for DNS and redirect them to the
  local recursor, or create a "redirected services" group which easily
  can be managed...)

Signed-off-by: Stefan Schantl <stefan.schantl@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>