EMANE per-interface configuration enhancements

```
Have a "defaults" or "remove configuration" button next to the "config
emane_ieee80211abg..." button in the Node Configuration dialog.

Another issue is clicking on the interface configuration after the WLAN
configuration has changed, the defaults are used. This could be solved with a
"copy config" button.
```

Original issue reported on code.google.com by `ahrenh...@gmail.com` on 14 Jan 2013 at 7:21

Start by locating the Node Configuration dialog and the existing "config emane_ieee80211abg..." interface configuration control. Check how WLAN changes and interface configuration values are stored, then define the behavior for defaults/remove configuration and copy config. Done means both requested controls work and interface configuration no longer unexpectedly reverts to defaults after WLAN changes.

Written by the indexing model from the issue text.