Vuln new countries

Summary:
  - migrate country primary key from implicit id to iso3 field
  - add a custom 'dbtransact' command to perform .sql file as transaction
  - new country data are available at http://ftp.openquake.org/oq-platform/vulnerability/

Test needs a 'master' installed with old country data (or development country data), upgrade to this branch and follow openquakeplatform/openquakeplatform/vulnerability/dev_bin/README.txt documentation
I don't want to diverge from the django way.