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...
as a general remark, the easyblock class is getting way too big, and this PR is not helping. ideally, `EasyBlock` only has `step` functions, everything else can be called from external functions (e.g. the fetch functions are 350 LOCs) or by making new classes with their own functions (eg the module handling is now 250LOCs).