-Changed behavior of SurveyServlet to just change the answerString of
TextAnswers
-AnswerEntityManager.findTextAnswerByParticipant_Question now just
returns an answer or null if no answer can be found.
-New Method Answer createEmptyStringAnswerForQuestion(Question question)
that creates and persists an Answer with an empty answerString for
question.
-Survey.jsp now only accepts UTF-8 encoded Strings.
-SurveyServlet calls request and response setCharacterEncoding("UTF-8")
to fix a bug with special characters.