IP info from bridge support

Fixes #74
Requires #65 to be merged in first
Also, in this case you can simplify the block by this:

```perl
if ($net->{bridge}) {
    $this_app->debug (5, "Device $sev is a bridge interface for bridge $net->{bridge}");
    $net = $config->getElement("/system/network/interfaces/$net->{bridge}")->getTree();
}
```

shorter and clearer. :smile: