Start reworking windows 2008 to do image-based installation

Currently, this update partitions the first hard drive, uses dism to
install the (currently hardcoded) Windows Server 2008 R2 Enterprise, and
try to run the unattended.xml to configure the system.  However, none of
the unattended.xml settings are actually applied, and you still have to
walk through the OOBE.)
Rework unattended.xml support for Windows 2008 R2

The unattended.xml we use for Windows 2008 needed a few fixups to work
properly when doing image-based installation.  With this set of fixups,
the Windows 2008 install requires zero intervention to get to a login
screen.
Merge pull request #30 from VictorLowther/start-windows-2008-r2-image-install

Start reworking windows 2008 to do image-based installation