LDAP login now returns status codes 200/401 instead of using
redirection.

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

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

If user is successfully logged in, store authentication in security context
else redirect to login page.

This bean will now be linked to a session returning different values for
different sessions and users.
It can be used to access current users (ARSnova)-session and user object.

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.

It is possible now to simulate LDAP login by requesting login page manually
but it needs some more internal changes to do all needed stuff for a real
ARSnova login.

triggered if no Referer-Header was sent.

API specification.

compatibility with third party frontends.

the header being present (e.g. with IE).

With this changeset the spring servlet configuration is separeted from the
application configuration. This will result in a main context and a servlet
context, holding only spring mvc information.

This change has a very nice side effekt: Spring AOP beans will be loaded
only once in application context, not a second time in mvc servlet context.

All relevant information about users (e.g. session mebership) are
accessible via UserService.
The method IUserService::getCurrentUser provides information about
the actual logged in user. If no user is logged in, this method will
throw a UnauthorizedException which will end up in 401 HTTP error.