Move NRML to a separate repository

[Lars Butler]

[et=4h]
[at=3.5h]

OpenQuake is no longer the only application making use of NRML (the GEM Modeler's Toolkit, for example). Thus, I think it is appropriate o 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.)

In the near future, we are going be more actively updating the NRML spec so it will be important to better maintain and tag the various revisions of NRML.

[Lars Butler (lars-butler)]

I found a way to copy a single folder of a git repo (with history and all) to another repo. This is useful since we want to break all of the openquake nrml schema & related artifacts out of the openquake repo (github.com/gem/openquake) and move it into the NRML repo (github.com/gem/nrml).

This article helped: http://palleas.com/2011/02/02/how-i-turned-a-folder-into-a-git-submodule/

[Lars Butler (lars-butler)]

Pull requests:
https://github.com/gem/nrml/pull/2
https://github.com/gem/nrml/pull/3
https://github.com/gem/nrml/pull/4
https://github.com/gem/openquake/pull/665