Added 2 classes (Square/Direction)

Area.java :
- Removed SIZEMAX/customSize.
- Defined a width and a height.
- Defined constructor.

Car.java :
- Added position (X,Y).
- Defined method moveCarX, moveCarY.

Direction.java (enum) :
- Defined 3 different values (LEFT/RIGHT/FIXED).

Game.java :
- Minor changes

Player.java :
- Defined constructor.
- Method getDirection().

Square.java (enum) :
- Defined 3 different states (EMPTY/USERCAR/BOTCAR) for the area
squares.