Extensible select and enumeration types

and their elements in schema Project_arm taking into account BASED_ON types


 date_or_date_time_item - EXTENSIBLE SELECT

 event_item - EXTENSIBLE GENERIC_ENTITY SELECT

 measure_value - EXTENSIBLE SELECT
          any_number_value
          any_string_value
          length_measure
          plane_angle_measure

 project_item - EXTENSIBLE SELECT