Modify App Image layout on Mac

Investigate and (hopefully) change the image layout on Mac. Why is the runtime image is placed under "PlugIns" directory?
   (Hello.app/Contents/PlugIns/Java.runtime/Contents/Home/)
Can we get that down to Hello.app/Contents/runtime/Contents/Home/ ?

Furthermore we need to clearly document the full layout of an application image as generated by jpackage on all three platforms