title: Doctrine doesn't generate inherited-class's properties
body: <p>I have one abstract MappedSuperClass and another class called "User" which is a child of this MappedSuperClass. The problem is that doctrine doesn't generate the User class's properties. Only the MappedSuperClass's properties. Why?</p>
  
  <pre><code>&lt;?php
  namespace IsCoconut\Models;
  use DateTime;
  use Doctrine\ORM\Mapping\Column;
  use Doctrine\ORM\Mapping\GeneratedValue;
  use Doctrine\ORM\Mapping\Id;
  use Doctrine\ORM\Mapping\MappedSuperclass;
  
  
  /** @MappedSuperclass */
  abstract class BaseEntity
  {
      /**
       * @var int
       * @Id 
       * @Column(type="integer") 
       * @GeneratedValue(strategy="AUTO")
       */
      protected $id;
  
      /** @Column(type="boolean")
       *  @var boolean
       */
      protected $deleted = false;
  
      /** @Column(name="creation_date_time", type="datetime")
       *  @var DateTime
       */
      protected $creationDateTime;
  
      protected function __construct()
      {
          $this-&gt;creationDateTime = new DateTime();
      }
  }
  </code></pre>
  
  <p>And this is my Entity which should be generated in database by Doctrine</p>
  
  <pre><code>&lt;?php
  namespace IsCoconut\Models;
  use Doctrine\ORM\Mapping as ORM;
  use Doctrine\ORM\Mapping\Entity;
  use Doctrine\ORM\Mapping\Table;
  
  /**
   * @Entity
   * @Table(name="users")
   */
  class User extends BaseEntity
  {
      /**
       * @var string
       * @ORM\Column(type="string", length=512)
       */
      private $forename;
  
      /**
       * @var string
       * @ORM\Column(type="string", length=512)
       */
      private $surname;
  
      /**
       * @var string
       * @ORM\Column(type="string", length=512, unique=true, nullable=false)
       */
      private $email;
  
      /**
       * @var string
       * @ORM\Column(type="string", length=512, unique=true, nullable=false)
       */
      private $passwordHash;
  }
  </code></pre>
  
  <p>This is output of <code>doctrine orm:schema-tool:create --dump-sql</code></p>
  
  <pre><code>CREATE TABLE users (id INT NOT NULL, deleted BOOLEAN NOT NULL, creation_date_time TIMESTAMP(0) WITHOUT TIME ZONE NOT NULL, PRIMARY KEY(id));
  CREATE SEQUENCE users_id_seq INCREMENT BY 1 MINVALUE 1 START 1;
  </code></pre>
  
  <p><strong>The User's class entity properties are missing!</strong> Why?</p>