Extensible select and enumeration types

and their elements in schema Required_resource_arm taking into account BASED_ON types


 classification_item - EXTENSIBLE GENERIC_ENTITY SELECT
          Required_resource
          Required_resource_assignment
          Required_resource_relationship
          Resource_item
          Resource_item_assignment
          Resource_item_relationship

 measure_value - EXTENSIBLE SELECT
          any_number_value
          any_string_value
          length_measure
          plane_angle_measure

 required_resource_item - EXTENSIBLE GENERIC_ENTITY SELECT

 resource_assignment_item - EXTENSIBLE GENERIC_ENTITY SELECT

 resource_item_select - EXTENSIBLE GENERIC_ENTITY SELECT