RFR 8170015: JShell: /help output looks terrible on a 100 column wide terminal

[Robert Field]

Please review...

Bugs:

     8170015: jshell tool: /help output looks terrible on a 100 column 
wide terminal
     https://bugs.openjdk.java.net/browse/JDK-8170015

     8170368: jshell tool: post setting not properly applied, line-ends 
not prefixed correctly
     https://bugs.openjdk.java.net/browse/JDK-8170368

Webrev:

     http://cr.openjdk.java.net/~rfield/8170015v1.webrev/

Thanks,
Robert