add some 'private'
finished model with test
Merge branch 'model_branch'

Conflicts:
	src/model/Dictionary.java
	src/model/Quiz.java
	src/model/TxtFileParser.java
	src/model/WordList.java
	src/model/test/DictionaryTest.java
	src/model/test/QuizTest.java
	src/model/test/WordListTest.java