UserService instead of a CouchDB request.

broadcasting it in reportSessionDataToClient method.

CouchDB and visited sessions.

Socket.IO.

requested.

interfere with the existing HTTP polling solution.

Some features still need to be ported:
- update session attribute lastOwnerActivity in CouchDB
- add session to visitedSessions in CouchDB
- check if session is locked

and the users inside of it

* rename methods to clearify that this are sockets

This provides smaller and cleaner Interfaces for each 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.

This layer can be used to create a StubDAO for use with unit tests.

* remove client from map on disconnect

* If a user posts new feedback, while having already posted one, the value
gets updated. This prevents feedback adding up.
* If feedback is too old (10 minutes), it gets removed. For testing
purposes the cleaning routine currently runs every few seconds, and
feedback only lasts a few seconds as well.
* The deleted feedback changes are broadcasted to:
	o All users, if feedback of other users has been deleted.
	o The user whose feedback got deleted.

Currently, this is a huge mess! There are three types of "Session Ids":
* The Socket.IO "session"
* The internal CouchDB session id
* The ARSnova session keyword

A severe clean up is needed before proceeding any further...

remove websocketcontroller and let sessioncontroller do the
authorization
add toString to User entity