RFR: JDK-8230654: jpackage package-type dmg on macOS

[Alexander Matveev]

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).

- Added link to "/Application" folder to DMG for drag and drop app to 
this folder.
- Added background image with arrow pointing from App icon to 
Application folder.
- If adding link and image to DMG fails it will not be considered 
critical error. In headless environment it might not work correctly.
- See JBS issue for screenshot on how DMG will looks like with this fix.

[1] https://bugs.openjdk.java.net/browse/JDK-8230654

[2] http://cr.openjdk.java.net/~almatvee/8230654/webrev.01/

Thanks,
Alexander