title: GreenDAO - primary key on multiple columns
body: <p>Does GreenDAO support primary key on multiple columns? </p>
  
  <p>I'm using <code>Property</code>'s method <code>primaryKey()</code> on two columns but it doesn't work. I'm getting exception: </p>
  
  <blockquote>
    <p>Caused by: android.database.sqlite.SQLiteException: table "table" has
    more than one primary key</p>
  </blockquote>
  
  <p>How to create primary key on multiple columns? Should I edit generated DAO classes?</p>