Improvements to i18n:
 * Instead of getting locale from metadata, get from filename.  All input
   files must be named <LANG>.json.
 * Skips input files named keys.json and qqq.json so the command line can include "*.json".
 * Outputs the next command line for the user to run.
 * Clarifies that we are using IETF, not ISO-639, language codes.

R=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/9604043

git-svn-id: http://blockly.googlecode.com/svn/trunk@928 c400ca83-b69d-9dd7-9705-49c6b8615e23