VS 2013 SDK and Shell download links

I have updated the page Resources about Visual Studio .NET extensibility to include the download links to:
  • Visual Studio 2013 SDK
  • Visual Studio 2013 Isolated Shell
  • Visual Studio 2013 Integrated Shell

and to include the link to the Visual Studio 2013 SDK MSDN documentation.

Remember that the VS 2013 SDK is now required to get the template for add-ins, as I explained here.