Fix: SignalR Authorize & Firefox Compatibility

Changes in architecture to support authorization and temporary
workaround for NTLM in Firefox (to be removed in SignalR 2.x). Thanks to
@davidfowl

Disco.BI/BI/Interop/SignalRHandlers/AdminAuthorizedPersistentConnection.cs

@@ -0,0 +1,16 @@
+using Disco.Models.Repository;
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Disco.BI.Interop.SignalRHandlers
+{
+    public class AdminAuthorizedPersistentConnection : AuthorizedPersistentConnection
+    {
+        private string[] authorizedUserTypes = { User.Types.Admin };
+
+        protected override string[] AuthorizedUserTypes { get { return authorizedUserTypes; } }
+    }
+}