Fixed loading of WinRT projects on a machine with only VS2013/Win8.1

This is a local change I have been keeping to allow me to load these projects.  It is also the change adamralph details in Issue #59.

Feel free to reject this if it is not a change you want to make, its just that I saw comments on other items indicating that VS2013/Win8.1 was going to be required for working with this branch, so I thought I would throw this this out there.