Update 3.0.0-preview2.md

Fix broken links (dotnet#2214)

Fix broken links (dotnet#2214)

Updated rel notes for issue number

Update releases.json

Merge pull request dotnet#2051 from dotnet/216rel

Adding 2.1.6/2.1.500 release for Nov 2018

Update to 2.2 release notes for isssue #

Release artifacts for 2.2 Preview3 (dotnet#2003)

Release artifacts for 2.2 Preview3 (dotnet#2003)

Merge pull request dotnet#1972 from dotnet/215rel

2.1.5 release content