rearranging components of DisplayPanel
adding JLabel to mark input field
adding GridBagLayout manager and wordNumberSpinner
userInputPanel now used left-aligned FlowLayout
resizing GUI frame
adding dynamically generated textfields to capture solution structure
fixing typo in invalid clue message
fixing cursor bug when invalid clue entered
adding setSourceClue and setSolutionStructure to Clue interface
renaming ClueImpl as ClueImplMarkA
adding new ClueImpl class. GUI now sets clue text and solution structure from separate user inputs
removing unused getNumberOfWords method from Clue interface, tidying ClueImpl
adding MouseAdapter and KeyAdapter to listen for Enter key press