RFR: JDK-8217687: jpackage --help improvements

[Andy Herrick]

Please review the jpackage fix for bug [1] at [2].

This is a fix for the JDK-8200758-branch branch of the open sandbox 
repository (jpackage).

JDK-8217687: jpackage --help improvements

Changes to help text, internal names, and several tests.

[1] https://bugs.openjdk.java.net/browse/JDK-8217687

[2] http://cr.openjdk.java.net/~herrick/8217687/webrev.01/