Overflaw

Results 2 issues of Overflaw

Method `getStaticLeases` Also complete create NAT command to check if provided IP part of static lease

For example [here](https://github.com/devgiants/livebox/blob/master/livebox/src/Devgiants/Command/WanInfosCommand.php#L52), if config file not found or not clearly defined, nothing is saying it.