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...
now that i start to understand this code, move these to `easybuild.tools.toolchain.mns` or `easybuild.tools.module_naming_scheme.toolchain`. the odds that they will ever be used for something other then mns are very very slim imho.