Allow setting WAN vlan/interface from gateway config.
A configuration without explicit definition of a WAN interface is
valid at the moment and results in the default configuration from
fff-network being used.
Originally, it was intended to automatically set WAN to vlan 2, if nothing was
specified. As this would break devices, which don't use swconfig for
WAN, the already configured WAN interface is left untouched.
Fixes: #85
Signed-off-by: Fabian Bläse <fabian@blaese.de>
Fabian Bläse