Dotnet 3.0 (#20) * .NET Core 3.0 support * Updated .NET Core 2.2 project references + Updated .NET Core 2.2 Dockerfile to reference latest MS images + Migrated Quick Starts to individual projects + Moved shared test code to shared folder for reducing duplications * .NET Core 2.2 quickstart update for JSON reference * Travis updates Updating to xenial; dotnet sdk 3.0 install * CHANGELOG Updates