Evaluate possible self-downloading packages

[lreimer]

Currently we expect all packages to be complete, software + ENV files.
The process of creating a package is nothing more than download + extract + customize.
What if the package only contains a script + small customizations. The rest is download on the fly.

[lreimer]

Best would be if the hook scripts would be full blown gradle.build files. Then the transition from the current way of building packages to self-downloading packages should be really small.

[lreimer]

https://twitter.com/DailyGradle/status/750343607144452096