Variable für Schwellwert zur richtigen Beantwortung einer Planquadratfrage im Backend implementiert.

CouchDBDao und Question-Entity um neue Attribute fuer Toggle Anzahl Markierungen aufheben erweitert.

Conflicts:
	src/main/java/de/thm/arsnova/dao/CouchDBDao.java

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version 0.41.0 had been replaced by newer 0.7x version wich includes some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.