Load non minified tinymce when in wicket development mode

For CKEditor we load full sources when wicket starts in development mode, see org.onehippo.cms7.ckeditor.CKEditorConstants#CKEDITOR_SRC_JS and the impl in that class.

This has been useful in developing plugins, finding bugs and during developing our fork of ckeditor.

For tinymce, we should add the option for retrieving and making available a non minified version.