Changed the ModuleRepository API slightly to ease respository management by ModuleManager.
Introduced LocalModuleRepository as an alternative; also useful for testing
Introduced a little ModuleWalker
Started with ModuleManagerTest to more easily test features such as preserve-cwd
documentation and other cleanup
Introduced VertxModule to provide easy access to a module config, but also its files. It's also nice for testing, as its now possible to simulate modules.