title: get all tables (classes) from realm
body: <p>I'm using Realm.io as database and I need a <code>select * from all_tables</code> in Realm.
  I mean a method returning an RLMArray, but I have not found anything about this.</p>
  
  <p>I need the class reference, such as Realm Browser.</p>
  
  <p>Thanks.</p>