Extensible select and enumeration types

and their elements in schema External_unit_arm taking into account BASED_ON types


 assigned_name_select - EXTENSIBLE GENERIC_ENTITY SELECT
          External_class_library

 external_identification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          User_defined_library_or_dictionary

 identification_item - EXTENSIBLE SELECT

 measure_value - EXTENSIBLE SELECT
          any_number_value
          any_string_value
          length_measure
          plane_angle_measure

 organization_or_person_in_organization_item - EXTENSIBLE SELECT