* Update samples to .NET Core 2.1

* Add Windows instructions

* Add instrucitons for macOS

* Simplify Windows instructions

* Update intro

* Add links to the new HTTPS topic

* Split out Windows instructions into separate topic

* Add instructions to use web browser

* Add link to sac2016 Dockerfile

* Add ASP.NET Core sample to samples/README.md

* Update SRI values per https://github.com/aspnet/templating/pull/521

* Add note or porting mapping errors