title: Single table per class hierarchy without discriminator column
body: <p>I have an existing table without discriminator column and I need to map it with single table hierarchy, how to map this?
  here is my table</p>
  
  <pre><code>vehicle
  ========
  vehicle_id
  manufacturer
  load_capacity
  passenger_capacity
  </code></pre>
  
  <p>I have 3 classes </p>
  
  <pre><code>Vehicle.java
  vehicleId;
  manufacturer;
  
  TransportationVehicle.java
  loadCapacity;
  
  PassengerVehicle.java
  passengerCapacity;
  </code></pre>