Missing os_type Windows2012 in version 0.4.5.1

[danmelton]

When building a base box for Windows 2012 with virtual box using VeeWee 0.4.5.1, the OS' do not include Windows2012_64 for virtual box, even though they are listed as being supported on https://github.com/jedi4ever/veewee/blob/master/doc/vbox.md

VBoxManage list ostypes

ID: Windows2012_64
Description: Windows 2012 (64 bit)
Family ID: Windows
Family Desc: Microsoft Windows
64 bit: true

This needs to be added too:

https://github.com/jedi4ever/veewee/blob/master/lib/veewee/config/ostypes.yml