title: Custom Control - how to encapsulate aggregation in another control
body: <p>I might be going around this wrong, but I want to create a custom control that is a subclass of sap.m.Dialog. This new control will have an aggregation 'leftImage' which will then be placed in a HorizontalLayout (private variable). However, this causes an error possibly because the 'leftImage' is already a dependent of my control.</p>
  
  <p>So how do I encapsulate an aggregation on another control?</p>