TODO
====

* Golden image / snapshotting / expandable VMs.
* Support more VBoxManage commands.
* Run vbox upgrade if available on all available instances.
* Iteration over a set of VMs.
* Support for upgrading VMs.
* Vagrant integration.
* Set window title using xdotool.
* Check for `/usr/bin/VBoxClient --clipboard` inside the guest.
* [host's resolver as a DNS proxy in NAT mode](https://www.virtualbox.org/manual/ch09.html#nat_host_resolver_proxy):
  `VBoxManage modifyvm "VM name" --natdnshostresolver1 on`.