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...
no, because then we'd have to import functionality from `easyconfig` in `toolchain.py` => cyclic import

I agree this looks a bit weird, but this construct of providing the module info to the toolchain from the outside is the only way