RFR 8161969, 8166637, 8154513, 8167552: jshell tool: ... truncation, welcome, /reload help

[Robert Field]

Please review the fix to these four bugs:

Bugs:

     8161969: jshell tool: /var value is not truncated per feedback setting
     https://bugs.openjdk.java.net/browse/JDK-8161969

     8166637: jshell tool: confusing truncation of long result values
     https://bugs.openjdk.java.net/browse/JDK-8166637

     8154513: JShell tool: welcome message should match feedback mode
     https://bugs.openjdk.java.net/browse/JDK-8154513

     8167552: jshell tool: Typo in jshell command '/? /reload' description
     https://bugs.openjdk.java.net/browse/JDK-8167552

Webrev:

     http://cr.openjdk.java.net/~rfield/8161969v0.webrev/

Thanks,
Robert