jpackage uses distinct create-app-image or create-installer modes to either create just an application image, just an installable package, or both.

It is requested we rework the jpackage CLI to not have two distinct "modes", and that we rename "installer" to "package" .

Here is my proposal to implement this:

1.) get rid of the mode, so the usage is just:
Usage: jpackage <options>
2.) rename option "installer-type" to "package-type"
3.) add the value "image" (or "image-only", "app-image", or "app-image-only") to the "package-type" option.
    If package-type is "image" then only the application image is created (as previously in "create-app-image" mode). Otherwise an installable package is created (as previously in "create-installer" mode.
    All the existing rules apply. If no "package-type" is given all supported packages on the platform will be created.
4.) adjust help and message text as appropriate.
5.) Build only one package. Designate a "default" package-type for each platofrm/subplatform and build that when package-type option is not used.

It was also mentioned that we might consider adding an option to preserve the application image when creating an installer. So far I don't see any significant benefit of this.