These checks will be done by service and security implementation if needed

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

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

No one will find it in method convertFileToByteArray.

The removed implementation used events wich were never published in any
part of the application.

This will send HTTP 501 NOT IMPLEMENTED error in case connector client is
used and not available.

This includes usage of newest connector-client. The last maven based
version 0.41.0 had been replaced by newer 0.7x version wich includes some
new features.

Having content negotiation with more than just JSON content
might follow REST principles.

All entities annotated with e.g. @XmlRootElement can be send as XML data.
This requires client to send Accept header with value "application/json"
to fetch JSON responses.
Default Accept header send by client is something like:
"text/html,application/xhtml+xml,application/xml"
which requests an XML document, not JSON document but JSON is expected.

This should enable annotation based cache-control header values.
Added a cache max age of 60 seconds to statistics resource. Proxy-Servers
should cache a statistics resource for about 60 seconds.