WebSocketSite serves also the flash policy file.

This removes the necessity of having aditional server listening on port 843, which required root priviliges. It can be done like this according to the article: http://www.adobe.com/devnet/flashplayer/articles/socket_policy_files.html.
Allow any capitalization of Upgrade header.

MSIE 10 and 11 send the value as "Websocket" while the other
browsers use WebSocket or websocket.