RFR: JDK-8043981 Remove the JPDA demo

[Staffan Larsen]

Please review this change to remove the legacy JPDA demos. These demos are quite dated at this point and the included instructions are incomplete. In addition the example/demo JPDA code does not fit well into the new modular structure because the source code is used for both jdb and for the demo.

bug: https://bugs.openjdk.java.net/browse/JDK-8043981
webrev: http://cr.openjdk.java.net/~sla/8043981/webrev.00/

Thanks,
/Staffan