The hardcoded string "Do Not Use" was being used in multiple places as the category...

The hardcoded string "Do Not Use" was being used in multiple places as the category for layers that shouldn't show up in the GUI menus.  Replaced it with a single #define'd string constant.  Also, there's no need to translate it, since the string is never displayed to the user.  Previously we were dependent upon the same translation for the string existing in both core and studio.

git-svn-id: http://svn.voria.com/code@1264 1f10aa63-cdf2-0310-b900-c93c546f37ac