support for hierarchical module naming schemes

@geimer: this should fix the problem that's blocking you right now

I might need to figure out one more thing w.r.t. the devel module name before this really works for you, I'm looking into that...
really, a decorator for a function that calls an external function? this just makes it horribly unreadable. and why isn't all of this defined in `easybuild.tools.module_generator`?