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

This affects:
* Some null checks before instanceof checks
* CouchDBDao.collectUnansweredQuestionIds()
* DeprecatedApiInterceptorHandler.getDeprecatedApiAnnotation()
* CacheControlInterceptorHandler.getCacheControlAnnotation()
* CacheControlInterceptorHandler.setCacheControlResponseHeader()
* FeedbackService - userService private field

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.

With this patch all feedbacks will be stored in memory without any
interaction with CouchDB. Due to in memory storage, all feedbacks will
be removed if server gets restartet.

Depending on new requests, feedbacks will be deleted after some time. 

With this patch, websocket feedback data will be send without using
UserService arrays within ARSnovaSocketIOServer except
reportDeletedFeedback().

These classes could be used to replace methods from DAO class.

and the users inside of it

The new NoContentException should indicate, that there is no error, but
the server could not provide a response object. This will result in
HTTP Code 204 - NO CONTENT => see RFC2616

Fixed two NullPointerExceptions wich might occure in QuestionService or
by using CouchDBDao from QuestionService.

This change is needed due to client developer restriction not to round
returned value on client side but on server side, because this would
change sth.

This change is needed due tu websocket security issues.

Method SessionService::broadcastFeedbackChanges is obsolete since this
method is used in FeedbackService.

FeedbackService::broadcastFeedbackChanges must not be annotated with
"@Authenticated" since authentication is not implemented for web sockets.

This provides smaller and cleaner Interfaces for each context.

cthelen recently

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.