Added & modified several message types.

Requests/Messages/Group.cs

@@ -0,0 +1,9 @@
+namespace HermesSocketLibrary.Requests.Messages
+{
+    public class Group
+    {
+        public string Id { get; set; }
+        public string Name { get; set; }
+        public int Priority { get; set; }
+    }
+}