Comment 0 for bug 904202

OpenQuake is no longer the only application making use of NRML (the GEM Modeler's Toolkit, for example). Thus, I think it is appropriate to maintain and version NRML within a separate repository. (This repository could also house common libs for parsers and serializers.)

Instead of maintaining a copy of the NRML schema (as we currently do in the OpenQuake repo in openquake/nrml/), we can simply add a git submodule in this location and reference a specific commit in the NRML repo. (Note from Lars: I've done a small experiment with this structure and the concept is sound.)