enable/disable identifier based on settings in conf

There is an issue in displaying identifiers on 'editable' search display. Identifiers are always editable regardless of how they are set in the configuration file (multipart_id_numbering). In this fix we solve this issue. Now, the identifier column will be disabled if 'editable' is set to 0 in the configuration file.  
Moreover, the identifier column will be disabled if identifier is a composite element, we implement this behavior because it is not yet clear how save operation will be performed for its composing elements.