Use both String and JLabel to the current keyboard layout

String is useful when passing the record to the Records class and JLabel is
used to update the current keyboard layout shown in the MainWindow.
Changes for menu entries

Most of the menus are changed to to-be-implemented
Use loadPreferences from the MainWindow class

This change is made because the MainWindow class should be the class that
controls the other classes.
Remove irrelevant TODOs
Add getCurrentLetter method
Clean up imports
Change start/stop/restart

The system time when starting/stopping is used so that there are less things
to do in the restart method. The calling of the start method is determined by
the running variable.
Don't use JScrollPane for now

The JScrollPane will be used once the program is finished debugging.
Add ChangeColor class

This class still contains syntax errors since the code is moved from the
changeColor method in the TypePanel class.