Fix bug which made deleting certain blocks throw an error, which then caused the page to be destroyed.  Also change empty strings to not create an empty title, and remove the last nulls from the language files.  Delete long-obsolete categories from procedures and variables.

R=spertus@google.com

Review URL: https://codereview.appspot.com/13366049

git-svn-id: http://blockly.googlecode.com/svn/trunk@1320 c400ca83-b69d-9dd7-9705-49c6b8615e23
Added i18n script js_to_json.py for translating core Blockly messages.
Moved code between xlf_to_json.py and common.py in support of change.
Changed Code.badXML message.
Generated files are included to insure that changes aren't significant.

R=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/13536043

git-svn-id: http://blockly.googlecode.com/svn/trunk@1321 c400ca83-b69d-9dd7-9705-49c6b8615e23