RFR 8154812: jshell tool: value printing truncation

[Robert Field]

(With updated webrev)

Please review configurable result value truncation.

Bug:
     https://bugs.openjdk.java.net/browse/JDK-8154812

Webrev:
     http://cr.openjdk.java.net/~rfield/8154812v1.webrev/

Thanks,
Robert