In local environment the principal must be casted to User object but in
production environment the username is represented as String in principal
object.

With this patch the application will try a cast to User object, if this
fails, it will do a cast to String - which holds the OpenID identifier.

This is needed if using index.html instead of developer.html

This file should be used to create a config file with matching values.

This websocket servlet class simply holds a list of connections and
broadcasts all incomming data to every connected client.

Include arsnova-legacy-js as overlay into resulting WAR archive.