Boot2Qt must not rely on fixed name of host-only network

From the Boot2Qt Documentation: "Create a new host-only network named vboxnet0 on Linux and VirtualBox Host-Only Ethernet Adapter on Windows."

This is not under the user's control. When creating a host-only network, VirtualBox assigns a name which the user can't change. In my case, the first such network is being named "VirtualBox Host-Only Ethernet Adapter #2" and further networks will get higher numbers. Boot2Qt can't work with any of these.

When there is no way to change the name in VirtualBox, there needs to be a way to select an existing network in Boot2Qt.