Refactoring of Question class and loading questions.

KvizServer/app/src/main/assets/multiple.txt

...rver/app/src/main/java/onlab/kvizserver/GameActivity.java

...er/app/src/main/java/onlab/kvizserver/QuizUpActivity.java

...p/src/main/java/onlab/kvizserver/model/GuessQuestion.java

...pp/src/main/java/onlab/kvizserver/model/PlayerAnswer.java

...er/app/src/main/java/onlab/kvizserver/model/Question.java