Remove English that leaked into other languages.

R=spertus@google.com

Review URL: https://codereview.appspot.com/12764044

git-svn-id: http://blockly.googlecode.com/svn/trunk@1254 c400ca83-b69d-9dd7-9705-49c6b8615e23
Add language en_us with "color" for "colour" for MOOC.
TODO: Copy into branches/mooc.

Review URL: https://codereview.appspot.com/12837049

git-svn-id: http://blockly.googlecode.com/svn/trunk@1255 c400ca83-b69d-9dd7-9705-49c6b8615e23
Update some Vietnamese messages

R=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/12739047

git-svn-id: http://blockly.googlecode.com/svn/trunk@1257 c400ca83-b69d-9dd7-9705-49c6b8615e23
Fix math_property block when input missing.

R=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/12851046

git-svn-id: http://blockly.googlecode.com/svn/trunk@1258 c400ca83-b69d-9dd7-9705-49c6b8615e23