Fixed Windows Bento box builds on Windows 8. Thanks to @adamedx for this fix, which I cargo-culted from the knife-windows project:

https://github.com/opscode/knife-windows/commit/d7b6efed3f03a56027d746b8fd093d15c3b176a4
Remove broken Windows 2012 definitions. These were copied from the Windows 2008R2 definition but don't actually build Windows 2012 boxes; they only build a Windows 2008R2 box.
Merge pull request #43 from juliandunn/windows-8-and-2012-fixes

Windows 8 and 2012 fixes