More improvements to messages in preparation for Hungarian
and other languages.
Added an option to Blockly.Block.prototype.removeInput() to avoid
throwing an exception if the input is not present.
Fixed copy-and-paste bug.

R=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/14300043

git-svn-id: http://blockly.googlecode.com/svn/trunk@1398 c400ca83-b69d-9dd7-9705-49c6b8615e23