distZip-style applications

This change adds support for distZip-style applications[1].  This
means applications that are packaged as a start script in bin/ and
classpath JARs in lib/ can be run.  This package can be created with
the Gradle application plugin, but also by the sbt-native-package
plugin.

[1]: http://www.gradle.org/docs/current/userguide/application_plugin.html

[#69255612]
Merge 69255612-dist-zip to master

[#69255612]