Extensible select and enumeration types

and their elements in schema Work_output_arm taking into account BASED_ON types


 activity_method_item - EXTENSIBLE GENERIC_ENTITY SELECT

 classification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          Work_output
          Work_output_assignment
          Work_output_relationship

 measure_value - EXTENSIBLE SELECT
          any_number_value
          any_string_value
          length_measure
          plane_angle_measure

 work_item - EXTENSIBLE GENERIC_ENTITY SELECT

 work_output_item - EXTENSIBLE GENERIC_ENTITY SELECT