Printing of array-valued elements

[Brian Goetz]

The toString() method on arrays is generally unhelpful (inherited from 
Object.)  Since jshell is a read-eval-PRINT loop, it might be nice to 
print the result of array-valued expressions in a friendlier manner, 
such as by using Arrays.toString(array) instead of array.toString(). 
(Might want to limit this to arrays of below a certain length.  (Might 
want to allow that limit to be set by preferences.))

So we'd get

  [ 1, 2, 3 ]

instead of

  [I at 2048230