Changed game design

- Added a sample crossword XML file

	renamed:    src/br/lusoft/android/wordmaster/core/Question.java -> src/br/lusoft/android/wordmaster/core/Clue.java
	modified:   src/br/lusoft/android/wordmaster/core/Crossword.java
	renamed:    src/br/lusoft/android/wordmaster/core/Answer.java -> src/br/lusoft/android/wordmaster/core/Word.java
	modified:   xsd/crossword.xsd