Enable pagination convention tests (#1659)

* Unskip pagination convention tests and rework exclusion property names
Also exclude Obsolete methods from pagination convention tests

* Reaction APIs appear to support pagination, flag to exclude for now and mark a TODO that they need implementing

* Repository invitation APIs need pagination implemented

* Exclude methods that use an alternative pagination approach

* Migrations, Licenses and References all need pagination implemented

* Pagination not supported for these methods (determined by API doc and poking the API) so exclude them from convention tests

* These methods need renaming to GetAll

* Rename offending RepositoryTrafficClient GetReferrers and GetPaths to GetAllReferrers and GetAllPaths

* Rename offending RepositoryBranchesClient methods from Get to GetAll

Octokit/Helpers/ExcludeFromPaginationApiOptionsConventionTestAttribute.cs

@@ -0,0 +1,15 @@
+using System;
+
+namespace Octokit
+{
+    [AttributeUsage(AttributeTargets.Method)]
+    public sealed class ExcludeFromPaginationApiOptionsConventionTestAttribute : Attribute
+    {
+        public ExcludeFromPaginationApiOptionsConventionTestAttribute(string note)
+        {
+            Note = note;
+        }
+
+        public string Note { get; private set; }
+    }
+}