Feature/userdata tracker (#271)

Added user data tracking logic
Added LastReceiveTime, SocketStatus and SubscriptionStatus properties to UpdateSubscription
Added SharedTransferStatus Enum and property to SharedDeposit
Added PositionMode property to SharedPosition model
Added IsZero property to SharedQuantity
Renamed IWebSocket LastActionTime to LastReceiveTime
Updated CryptoExchangeWebsocketClient LastReceiveTime logic
Updated Subscription status change event handler to run sync instead of separate task

CryptoExchange.Net/Sockets/Default/Interfaces/IWebsocket.cs

@@ -69,6 +69,10 @@ namespace CryptoExchange.Net.Sockets.Default.Interfaces
         /// </summary>
         bool IsOpen { get; }
         /// <summary>
+        /// Last timestamp something was received from the server
+        /// </summary>
+        DateTime? LastReceiveTime { get; }
+        /// <summary>
         /// Connect the socket
         /// </summary>
         /// <returns></returns>