Restore address lookup by VirtualBox UUID

A small change to `address_for` that matches against old UUID values if
present.
Release addresses allocated by VirtualBox UUID

This is a partial revert of 9b7a673 as it restores a `hook.before` on
`VagrantPlugins::ProviderVirtualBox::Action::Destroy`. This allows us to
release VirtualBox UUID allocations from the Pool before the Destroy action
removes the UUID from a machine.
Merge pull request #13 from Sharpie/restore-uuids

Restore functionality to VirtualBox UUIDs