[Feature] Add support for vm.name for virtualbox

[gena01]

Please add support for "vm.name=" syntax. See documentation here: https://www.vagrantup.com/docs/virtualbox/configuration.html#virtual-machine-name

This came up after I upgraded from chefdk1.x to the latest stable 3.1.0 release which includes the new ktichen-vagrant. One of the things I noticed was that this commit: 1f58fce
was made to fix a path restriction.

The side-effect is that in VirtualBox GUI you can not tell which cookbook the VM is built-against. Adding something like:
vm.name= "kitchen-#{File.basename(config[:kitchen_root])}-#{instance.name}"
would help and restore the naming in VirtualBox GUI and hopefully address both issues.