First refactoring to provide multiple debian packaging strategies

This is the first refactoring step to provide an additional java-based debian packaging implementation.
Does this look okay from the coding side? @jsuereth , @kardapoltsev , @aparkinson ?

I basically introduced two new task `debianJDebPackaging` and `debianNativePackaging`.
You set the packaging strategy with `packageBin in Debian <<= debianJDebPackaging in Debian`.
Right now, depending on the pgpPlugin may not be "safe to do", we should have a big auto-plugins discussion across the plugin authors to see what kinds of conventions/dependencies we'd liek to expose and how we do so.