Add reactions to issue, commit comment and review payload (#1405)

* add reactions to issue response payload

* add reactions to commit comment payload

* add reactions to review comment payload

* create tests for issue client

* tests for commitcomment client

* tests for pull request review comment

* change observable tests

* simplify strings

* remove unnecessary clients

* change integration tests to retrieve all reaction types

* create integration test for issue comment client

* fix merge conflicts

* fix merge conflicts

* gets tests passing again

* fix some reaction integration tests

* Fixup unit tests wth preview accepts header
Also applied preview header to a couple of repositoryId based calls that were added by another PR

* Fixup unit tests wth preview accepts header
Also applied preview header to a couple of repositoryId based calls that were added by another PR

* Rework reaction payload tests for IssueComments to handle Get, GetAllForIssue and GetAllForRepository calls

* [WIP] reaction payload tests

* Rework reaction payload tests for IssueComments to handle Get, GetAllForIssue and GetAllForRepository calls

* Rework reaction payload tests for Issues client

* Rework reaction payload tests for PullRequestReviews client

* Rework reaction payload tests for CommitComments client

* Revert "[WIP] reaction payload tests"

This reverts commit a6179b0f21a3ddfe36bfd3ae5eafae0e69b52252.

Octokit/Models/Response/PullRequestReviewComment.cs

@@ -102,6 +102,8 @@ namespace Octokit
         /// </summary>
         public Uri PullRequestUrl { get; protected set; }
 
+        public ReactionSummary Reactions { get; protected set; }
+
         internal string DebuggerDisplay
         {
             get { return string.Format(CultureInfo.InvariantCulture, "Id: {0}, Path: {1}, User: {2}, Url: {3}", Id, Path, User.DebuggerDisplay, Url); }