Add snippets.erl
Fix ssh/DHCP/network interface mapping

This sets a persistent mapping between the VirtualBox adapters
and Linux interface names.
I.e. now every time the VM is booted its Adapter 1 will be eth0,
and Adapter 2 will be eth1.

Assumption: I rely on the driver type uniquely identifying the
NIC/adapter; don't use two adapters of the same kind!