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

22 preview2 release artifacts (dotnet#1937)

* Adding 2.2 Preview 2 Release artifacts

Update Issue #

Updated links for symbols