Build and use arrays of Java objects.

The demonstrated predicates are:

• array_set(+Array, +Index, +Value)
  set a value: Array[Index] = Value
• array_get(+Array, +Index, -Value)
  return a value: Value = Array[Index]

• create_array(+Class, +Size, -Array)
  make a new array of class Class and dimension Size resulting object is unified with the last argument

• expand_array(+Array, -List)
  converts a Java Array into a Minerva List