implement: via two booleans you can now decide whether AnswerStatistics and FeedbackQuestions shall be exported, too

add constructors to transport classes to parse "main"class

 - add controller/service/entity/dao-functions
 - add motdlist so that users can tell the backend, which motds they have read
 - add admin account (in arsnova.properties: security.adminaccount).
 - add permission function for admin

Requesting partial lists would interfere with Spring caching so
pagination is handled by the newly introduced PaginationListDecorator
in the controllers. This additionally allows to determine the total
count of items (independent from pagination parameters) which is not
possible with CouchDB.

change getQuestionsBySortOrder to fetch Questions in one single db request instead of requesting every document alone

#15362 alphabetical sortOrder is now automatically created when there is no sortOrder. bugfix included

#14886 edited the lecture/preparation view to use new sort_question-views, saveOrder is not checking whether there is already a list

#14886 edited the lecture/preparation view to use new sort_question-views, saveOrder is not checking whether there is already a list

Removed test cases because they weren't of much use after
the refactoring.

This will result in events being fired at the right time.
Most importantly, this ensures event-specific caching
annotations to work correctly.

getSession throws an HTTP exception, which is not
good style. Additionally, as it calls
getSessionFromKeyword internally -- which has a caching
annotation -- this caching mechanism will not work
because it only works if the method is called
from another object. This is due to the way Spring
is using proxies to intercept the calls.