Added TODOs to keep track of methods still evicting the whole answers
cache for future improvements. Additional refactoring is necessary to
implement these.

Direct method calls bypass the caching proxy if AspectJ weaving is not
configured.

If deleted documents remain in the sort order,
this will crash the application. We simply skip
over any documents we could not load.

With this fix, deleted documents may remain
in the sort order without a problem. Once the
order is updated by the teacher, any deleted
documents will be removed.

This may cause 'lagging' statistics, but that
should not be a problem.

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

Task #14410

It can occur that the timed event of piRound deactivation will not be
called (server crash/restart). With this fix the activation will be
canceled on question document when the endtime has been exceeded. Task
#14410

fix Parameter in getQuestionSortType and getSubjectSortType; Function expected the questionVariant, instead got a boolean(in a String)