JMC-6461: Cleaner versioning information when not embedding a JDK

[Marcus Hirt]

Hi all,

Please review this change to clean up the about box versioning
information when not embedding a JDK (seems to be the path that 
most vendors have chosen).

Jira:   https://bugs.openjdk.java.net/browse/JMC-6461
Webrev: http://cr.openjdk.java.net/~hirt/JMC-6461/webrev.0/

Kind regards,
Marcus