Added Visual Studio extension

I've added a Visual Studio 2012/2013 extension in its own folder. All you need to be able to open a Visual Studio extension project is the Visual Studio SDK which is a free download from here: http://www.microsoft.com/en-us/download/details.aspx?id=30668

The extension is self-contained and doesn't interfere with your current repo - it just adds a folder with the project inside it.

This fixes issue #5 and #8