Support loading modules from a single JAR

For embedded use cases, it's important to be able to package modules up into a JAR. We should have some local loader which can perform module loading from a repository located within a JAR. This repository would only support file loading though, since loading JARs within JARs is problematic. This means that to assemble a module repository JAR, one would have to unroll each constituent JAR into it (i.e. convert JARs into directories). This should be supported via tooling i.e. a Maven plugin and an Ant task, plus whatever weird stuff Gradle uses.