display class code refactor [2.10.0]

This version introduces multiple enhancements:

small code refactor for core codes
changed methods name convention

Details of additions/deletions below:
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Modified:   /BLUE_FRAMEWORK/packages/CORE/display_class.php
            -- Added --
                _getLanguageCode to return language code for url in mode rewrite or classic url mode
            -- Updated --
                render method name
                method clean to _clean name
                _path to use new method _getLanguageCode