Small Game & Code Improvements

[TheRealLyonic]

Various small changes to improve the gameplay-loop and add more code readability. Among these changes are a 'restart' option for when the game is over, a new basic icon for the game's JFrame, and some small graphical changes (I.e. a red apple as opposed to a green one). Some comments were added throughout the Board class, and a number of variables were renamed to both better fit Java practices and to better reflect their purpose within the program. Hope you find these changes to your satisfaction!