 base <code>ICommand</code> implementation that executes other <code>ICommand</code>s.
   
  <P>
  A <code>MacroCommand</code> maintains an list of
  <code>ICommand</code> Class references called <i>SubCommands</i>.</P>
  
  <P>
  When <code>execute</code> is called, the <code>MacroCommand</code> 
  instantiates and calls <code>execute</code> on each of its <i>SubCommands</i> turn.
  Each <i>SubCommand</i> will be passed a reference to the original
  <code>INotification</code> that was passed to the <code>M