Remove dedicated V3 messages.

Source/MQTTnet/Packets/MqttConnAckPacket.cs

@@ -1,6 +1,19 @@
-namespace MQTTnet.Packets
+using MQTTnet.Protocol;
+
+namespace MQTTnet.Packets
 {
-    public abstract class MqttConnAckPacket : MqttBasePacket
+    public class MqttConnAckPacket : MqttBasePacket
     {
+        /// <summary>
+        /// Added in MQTTv3.1.1.
+        /// </summary>
+        public bool IsSessionPresent { get; set; }
+
+        public MqttConnectReturnCode ConnectReturnCode { get; set; }
+
+        public override string ToString()
+        {
+            return "ConnAck: [ConnectReturnCode=" + ConnectReturnCode + "] [IsSessionPresent=" + IsSessionPresent + "]";
+        }
     }
 }

Source/MQTTnet/Packets/Properties/MessageExpiryIntervalProperty.cs

@@ -4,7 +4,7 @@ namespace MQTTnet.Packets.Properties
 {
     public class MessageExpiryIntervalProperty : FourByteIntegerValue
     {
-        public MessageExpiryInterval(uint value) 
+        public MessageExpiryIntervalProperty(uint value) 
             : base((byte)PropertyID.MessageExpiryInterval, value)
         {
         }

Source/MQTTnet/Packets/V3/MqttV3ConnAckPacket.cs

@@ -1,16 +0,0 @@
-using MQTTnet.Protocol;
-
-namespace MQTTnet.Packets.V3
-{
-    public class MqttV3ConnAckPacket : MqttBasePacket
-    {
-        public bool IsSessionPresent { get; set; }
-
-        public MqttConnectReturnCode ConnectReturnCode { get; set; }
-
-        public override string ToString()
-        {
-            return "ConnAck: [ConnectReturnCode=" + ConnectReturnCode + "] [IsSessionPresent=" + IsSessionPresent + "]";
-        }
-    }
-}