Notifications can be tested

Notification ImplementationType was added for showing in UI (Humanized/Title cased of Implementation)

NzbDrone.Core/Notifications/Prowl/InvalidApiKeyException.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+
+namespace NzbDrone.Core.Notifications.Prowl
+{
+    public class InvalidApiKeyException : Exception
+    {
+        public InvalidApiKeyException()
+        {
+        }
+
+        public InvalidApiKeyException(string message) : base(message)
+        {
+        }
+    }
+}