title: CKEditor plugin button disabled in source mode
body: <p>I was trying to add my own toolbar button in CKEditor (inside vBulletin). Following is my Code:</p>
  
  <pre><code>CKEDITOR.plugins.add( 'app',
  {
  init: function( editor )
  {
      editor.addCommand( 'AppWidget',
          {
              modes : { source : 1, wysiwyg : 1 },
              exec : function( editor )
              {   
                  alert("foo");
              }
          });
      editor.ui.addButton( 'app',
      {
          label: 'App Widget',
          command: 'AppWidget',
          icon: this.path + 'app.png'
      } );
  }
  } );  
  </code></pre>
  
  <p>Problem is: It will show in WYSIWYG mode, but will be disabled (greyed out) in source mode. But I need this button to be enabled in source mode. If I write:</p>
  
  <pre><code>modes : { source : 1 },
  </code></pre>
  
  <p>it will be disabled in both modes.</p>
  
  <p>Any hints on this here? Thanks in advance.</p>