Added a constant REQUEST_URI to check RewriteRule processing.
Added a new utility function _self($args=array(), $lang='') equivalent to _url(NULL, $args=array(), $lang='');
Added a new utility function _getLang() to manage contents by language,
Updated the utility function _getTranslationStrings() to return a single-value field "^^_i18n" when the third argument "$lang" is provided.
And data object will be returned if object is provided.
Updated _js() and _css() to check the file existence. If the file does not exist, nothing is printed.
Bug fix for javascript error showing when there is no site warning message.