Add support for WebSocket server via ASP.NET Core 2.0

Tests/MQTTnet.TestApp.AspNetCore2/Program.cs

@@ -0,0 +1,18 @@
+using Microsoft.AspNetCore;
+using Microsoft.AspNetCore.Hosting;
+
+namespace MQTTnet.TestApp.AspNetCore2
+{
+    public static class Program
+    {
+        public static void Main(string[] args)
+        {
+            BuildWebHost(args).Run();
+        }
+
+        private static IWebHost BuildWebHost(string[] args) =>
+            WebHost.CreateDefaultBuilder(args)
+                .UseStartup<Startup>()
+                .Build();
+    }
+}