Connector bean has to be disabled because connector could not get any
connection to database server. Connection to database server is
forbidden.

It is required to setup those values after login. Current session
information will be set up after joining a session.

Renamed TEACHER to SPEAKER to adapt roles to ARSnova client, and
also added some convenience methods for role handling.

These URIs should not be requested if user does not successfully join a
ARSnova session.

One more thing that allready should have been in documentation but
drives developers and admins into madness.

This should prevent concurrent ConcurrentModificationException after
application lock on undeploy.

This patch intends to close all websocket connections on bean
destruction of ARSnovaSocketIOServer.

This reverts commit c22330fd.

This enables access to all UserSessionService objects from within the
application. This could be used to send events to all session users.