RFR: JDK-8231856: pkg installer dialog contains background image which does not look correct

[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).

- Fixed by using correct icon for pkg.
- Added icon for dark theme and it will be called 
appName-background-darkAqua.png, for separate customization between 
light and dark theme.
- pkg xml will be written using XML APIs.
- See JBS for screenshots on how pkg will look like.
- MAC_CF_BUNDLE_IDENTIFIER will be used instead of IDENTIFIER, since 
MAC_CF_BUNDLE_IDENTIFIER is correct value to use after JDK-8231281.

[1] https://bugs.openjdk.java.net/browse/JDK-8231856

[2] http://cr.openjdk.java.net/~almatvee/8231856/webrev.00/

Thanks,
Alexander