Added remaining gateway events, added IAudioChannel, added CacheModes

src/Discord.Net.WebSocket/Entities/Channels/ISocketPrivateChannel.cs

@@ -0,0 +1,9 @@
+using System.Collections.Generic;
+
+namespace Discord.WebSocket
+{
+    public interface ISocketPrivateChannel : IPrivateChannel
+    {
+        new IReadOnlyCollection<SocketUser> Recipients { get; }
+    }
+}