Added useLegacyV2RuntimeActivationPolicy

Added useLegacyV2RuntimeActivationPolicy="true" to the Startup section
of the config so that we can get .net dependencies to load if/when
required.

MediaBrowser.ServerApplication/App.config

@@ -15,7 +15,7 @@
     <add key="ProgramDataFolderName" value="MediaBrowser-Server" />
     <add key="ClientSettingsProvider.ServiceUri" value="" />
   </appSettings>
-  <startup>
+  <startup useLegacyV2RuntimeActivationPolicy="true">
     <supportedRuntime version="v4.0" sku=".NETFramework,Version=v4.5" />
   </startup>
   <runtime>