Add ability to run a JAR as a module

Basically this amounts to creating a JAR module loader on boot, which uses the "Dependencies" MANIFEST property to establish initial dependencies.

Implement via a -jar CLI option, which makes the final argument into a JAR file instead of a module name. The JAR file can reference modules in the LocalModuleLoader.

The Class-Path of the executed JAR should be respected, unless -ignore-class-path is specified on the command line.