title: using connection manager with orm cakephp 3
body: <p>Every tutorial or documentation regarding this subject is used with sql queries but never with new orm.
  I have two data sources defined in config/app.php: default and not_default
  with same tables and columns, when the user login the default database is connected.
  when the user clicks a certain button i need to change the connected database to not_default:</p>
  
  <p>I achieved this so far:</p>
  
  <pre><code>ConnectionManager::get('default')-&gt;disconnect();
  ConnectionManager::get('not_default')-&gt;connect();
  ConnectionManager::get('not_default')-&gt;begin();  //dont know if required
  </code></pre>
  
  <p>when doing this: <code>echo ConnectionManager::get('not_default')-&gt;isConnected();</code> I get 1 for not_default and 0 for default so it is connected 
  but the problem is when getting the model's TableRegistry the connectionname is still the default one!! How to change it???</p>
  
  <p>I want to be able to get data using orm from database other than the default one.</p>