Add run as user and specific resov.conf

[jerome-labidurie]

This PR add 2 new functions to alternetworking script :

• possibility to start the command with another user, using sudo
• usage of a different resolv.conf file than the one from /etc This is usefull if your VPN configure specific nameservers that are not accessible from outside of it.

I've also corrected a small bug for --clean short option

best regards