Remove Some Walls to Form a Maze

Adding cell methods for removing walls

To generate a maze, MazeGenerator has to remove some walls. First, MazeGenerator will need a way to find which cells have not been added to the maze yet. In other words, it needs to identify which cells still have all four walls.

1. In Cell.java, add a public method called hasAllWalls(). It should take no parameters and return a Boolean value.
2. Add a Boolean called allWalls which is true if every element in the wall is true using logical operators to compare the contents of each element.
3. Return allWalls.

    ...
 
  ________________ hasAllWalls(______) {
    _______________ allWalls = ________ && ________ && ________ && ________;
    return ________;
  }
    ...