Background: See #3721 (comment)
tl;dr: This should build the assemblies in a way that they are portable to all the supported Linux x64 platforms for .NET, but requires that we package native binaries which dotnet publish will publish.

• Update build so it can build and publish for the runtime linux-x64
• Update packaging script to package native binaries published and remove unneeded dependencies
• Work with Microsoft Repo owners to develop a package publishing story. @raghushantha and @TravisEz13 can get you started here.
• Update documentation
• Create .tar.gz package for Linux
• Add documentation about Linux package dependencies
• Update docker files
• Update from 2.0.0-preview1-002106-00 to 2.0.0-preview2-25303-04 that includes Fix SSL on Debian 9 dotnet/corefx#19070 to support Ubuntu 17 and Debian 9 (update: powershell has moved to official .NET Core 2.0 release)