The .csproj rewriting is a bit too eager in removing nodes

[kcragin]

I wasn't able to build after upgrade because C# targets were removed by your .csproj rewriter:

  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />

It looks like this bit of code in NuGetUpgraderPackage.cs:

186    //RWM: Remove any Package Targets. 
187    targets.Where(c => c.Attribute("Project").Value.Contains(row.Attribute("id").Value)).ToList() 
188           .ForEach(c => c.Remove());