documentation
added Chapter 3's configuration info
Refactored QuizBean:
* renamed methods: (getAnswer -> getAnswerToLastQuestion, startOver -> init)
* refacted answerAction method
* Problem POJO no longer has isCorrect method
added Chapter 4 configuration info
merged variable declarations
* corrected typo
* removed stylesheet file, wasn't being used
formatting
* added documentation
* rearranged Chapter 4 sample programs in the order that they are presented in the book
removed files that weren't being used
added missing stylesheet file