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...
does this imply that using `os.environ` in easyblocks (or framework) is a big no-no? (and how do you unset a variable, is that not tracked at all?)