These events add more detail about what specific
action just happened.

Unlock is a better representation because this event only
occurs when multiple questions are published. 'New' should
only be used when questions are created.

Check user object against null before accepting feedback via Websocket.

Task #15666
Task #15693

Just for consistency.

The delayed pi-round change can now be triggered via a simple api call.
After the api call a timed task will be started, which executes the
necessary steps for a round change. 

Events for all learning progress related actions
are generated, like answering a new question.
The event classes are used as a tag to evict
the cache based on the session.

A NotFoundException was mistakenly thrown when the Session was set to
null via Socket.IO. Additionally, the user count was sent before it
had been updated.

count to NewAnswerEvent websocket broadcast. Task #14471

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

#14099