Added a trace listener for initialization errors/warnings to the sample

- So far this only listens to the SignalR.ReflectedHubDescriptorProvider key

samples/Microsoft.AspNet.SignalR.Samples/Web.config

@@ -71,13 +71,19 @@
           <add name="SignalR-Transports" />
         </listeners>
       </source>
+      <source name="SignalR.ReflectedHubDescriptorProvider">
+        <listeners>
+          <add name="SignalR-Init" />
+        </listeners>
+      </source>
     </sources>
     <switches>
       <add name="SignalRSwitch" value="Verbose" />
     </switches>
     <sharedListeners>
       <add name="SignalR-Transports" type="System.Diagnostics.TextWriterTraceListener" initializeData="transports.log.txt" />
       <add name="SignalR-Bus" type="System.Diagnostics.TextWriterTraceListener" initializeData="bus.log.txt" />
+      <add name="SignalR-Init" type="System.Diagnostics.TextWriterTraceListener" initializeData="init.log.txt" />
     </sharedListeners>
     <trace autoflush="true" />
   </system.diagnostics>