RFR: JDK8221777: CLI changes from jpackage EA5 feedback

[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).

This change renames the "create-image" mode to "create-app-image", and 
removes the "--files" options .


[1] https://bugs.openjdk.java.net/browse/JDK-8221777

[2] http://cr.openjdk.java.net/~herrick/8221777/ 
<http://cr.openjdk.java.net/%7Eherrick/8221777/>

/Andy