Had to fix CouchDBDao.getSessionFromId() to implement working permission
evaluation.

This small method had thrown net.sf.json.JSONException wich causes
Spring to send HTTP 405 - Method not allowed and block request.

There was a bug in the session retrieval code causing an exception.

There was a bug in the session retrieval code causing an exception.

Note that this is currently untested. :o

Introduced a new CouchDB view method, and a new field to divide
'skill_questions' into preparation, lecture, and flashcard
variants. The former question type 'flashcard' will be removed
soon.

**/lecturerquestion/{questionId}/answer/ for free text answers.