Update samples to work in Dev16 and obtain packages from NuGet

[gregg-miskelly]

For Dev16, Concord extension API and tools are now packaged in easier to use nuget packages. This updates the samples to obtain them from there.

This also makes a few other fixes/improvements:

• Make projects buildable/runable in Dev16
• Use 'PackageReference' to download packages instead of packages.config
• Remove source control disable properties
• Add a README.md for the Iris directory

[plnelson]

👍 Thanks!