Udev rules to automatically call rfkill unblock wifi when new network
devices are added. Some drivers seem to default to blocked state which
is really not wanted.
Some wifi drivers create eth* interfaces, so call rfkill unblock also
for those.
Get back the /etc/rc.local rfkill call for now.
Merge pull request #27 from opinsys/unblock-wifi

Make sure wifi interfaces are not soft blocked when they come available

Wifi cards on some laptop models seem to be soft blocked by default which confused users. Add a udev rule to call "rfkill unblock wifi" when new network interfaces are initialised. This needs to be called also for ethX devices as some wifi interfaces use eth in their naming. Better filter should be doable, but this works for now. In addition to dynamic calling, call rfkill also from /etc/rc.local to make sure that it's called at least once during the boot. If the interface does not exist at this point, it has no effect, though.