contrib/nmbug: add nmbug-status script

This is (almost) the same script as has been used for
http://nmbug.tethera.net/status for a while now. The only change is
that the configuration is not hardcoded anymore. By default the config
is fetched from a special branch in the nmbug repo that contains only
config info. The idea is that push access to this branch can be
restricted a bit more than the tags, since it will change the
appearence of the web pages.