Changing the Session object the way it was done previously
interferes with the new caching mechanism. The objects are
now long-lived so any direct changes to it which are not
in the spirit of its use case have to be removed. In this
case, changing the creator information invalidated many
of the isCreator checks sprinkled through the code, as
the new creator's name would have been the string
"not visible to you."

Added few pp Attributes to SessionInfo. Requests for Public Pool Sessions now return SessionInfo instead of Session.

Updated copyright year and adjusted header format to be consistent over
all files and with other ARSnova projects.

The creator name is only visible to the creating user itself.

SessionController: Append integer to a string will result in a string
ApplicationPermissionEvaluator: Code formatting
UserService: Create new user object instead of assining parameter reference
ARSnovaSocketIOServer: No exceptions are thrown

Spring security based permission check will do this for us.

This sets current user and ARSnova session information in a session
scoped service bean. If the user connects with a websocket, the
websocket session ID will be set in addition to the user and session
object.

The aspects methods pointcut after returning from joinSession() method
in SessionService. So the UserSessionService will be set with all needed
data after a user successfully joins a session.

With this service available, it can be used to replace some usage of
Array/Map based application wide data structures that cause some trouble
when stopping or redeploying the application.

This bean holds user and session object of the current user after he
joins a session and could be used to access those objects within the
application.

Added two simple URIs to get a JSON representation of the referenced
objects.