Implement project Essential_L16.1 (Object class)

@kostiantyn-kuzin please review
To show that it indeed compares the sides but not the objects use the following code:
var b3 = new Block(1, 2, 3, 4);
Console.WriteLine(Object.ReferenceEquals(b1, b3)); // should be false
Console.WriteLine(b1.Equals(b3)); // should be true