Fixed XmlDocument GetProperty to check for user properties 'invariantly'.

Added a method on content to remove the file persistence queue just before it's written based on the module, this should hopefully speed things up and fix some potential issues.
Added an overloaded method on library for UpdateDocumentCache which should save on a few dozen sql calls when publishing a node since we already have
the Document object reference yet we were looking it up again for no reason.

src/Umbraco.Web/UmbracoModule.cs

@@ -164,6 +164,7 @@ namespace Umbraco.Web
 		{
 			if (content.Instance.IsXmlQueuedForPersistenceToFile)
 			{
+				content.Instance.RemoveXmlFilePersistenceQueue();
 				content.Instance.PersistXmlToFile();
 			}
 		}