Move config from /etc/firewall to /etc/ifw

Also change dump file name to /var/log/ifw.dump
Remove now unneeded mports config.
Improve DNAT and its configuration

Move DNAT configuration to 'ports' file.
Make port DNAT'ed if its type is like "IP:PORT".
Automatically allow forwarding this port in.
Config file name change: if -> links

Also change some variables' names
$FW -> $CONFIG
$INTERFACES -> $LINKS
Merge branch 'dev'