Firewall: DNAT - Show right DNAT interface in ruletable

Firewall: DNAT - Show right DNAT interface in ruletable

Now:
When using a hostgroup as source there are all corresponding DNAT
interfaces shown in ruletable depending on the entries in the group.

When in DNAT area "-automatic" is selected, the DNAT interfaces are
shown as IP-Addresses, else they are shown as "ORANGE","GREEN","BLUE"...

BUGFIX: When there is a MAC address used in a sourcegroup, the rules could not be set. Now MAC addresses get allways the public interface as DNAT