Simple way to prevent certain content types from using a wysiwyg editor

This allows an administrator to disable the wysiwyg editor on select content types by adding a no_wysiwyg=true param to the content type.

This is needed because CKEditor sometimes thinks it's better than the person writing the content and rewrites the HTML.
Yes, that would be a better way to implement the checking (Rather than the hacky changing of the ID). Will get to that now.

I've made a change that makes the enabling/disabling of wysiwyg for a content type easy to get to, rather than being an arcane and hidden (imo) parameter.