display_class lopp in optional marker fix

This version introduces multiple enhancements:

fixed problem when data loop was in optional marker, when rendering whole loop generated data was removed

Details of additions/deletions below:
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Modified:   /BLUE_FRAMEWORK/packages/CORE/display_class.php
            -- Updated --
                _clean, turn on loop clean and moved before optional clean
                _cleanMarkers added removing loop start and end markers