title: Grails "One to Many" relationship without a table join
body: <p>I'm new to Grails and GORM and I try to implement a "One to Many" relationship.
  I tried the example in the doc :</p>
  
  <pre><code>class Book {
      String title
  }
  class Author {
      static hasMany = [books: Book]
      String name 
  }
  </code></pre>
  
  <p>Here are the tables that are generated :</p>
  
  <pre><code>AUTHOR
  - Id (PK)
  - Name
  
  BOOK
  - Id (PK)
  - Title
  
  AUTHOR_BOOK
  - Author_Books_Id
  - Book_Id
  </code></pre>
  
  <p>I was expecting something more like :</p>
  
  <pre><code>AUTHOR
  - Id (PK)
  - Name
  
  BOOK
  - Author_Id (PK)
  - Book_Index (PK)
  - Title
  </code></pre>
  
  <p>Is there a way to achieve this (get rid of the join table) ?</p>