Implementation for the minimize ribbon button.
Inheritance: ComponentFactory.Krypton.Toolkit.ButtonSpec
 private void CreateButtonSpecs()
 {
     // Create fixed button specifications
     _buttonSpecsFixed   = new RibbonButtonSpecFixedCollection(_ribbon);
     _buttonSpecClose    = new ButtonSpecMdiChildClose(_ribbon);
     _buttonSpecRestore  = new ButtonSpecMdiChildRestore(_ribbon);
     _buttonSpecMin      = new ButtonSpecMdiChildMin(_ribbon);
     _buttonSpecMinimize = new ButtonSpecMinimizeRibbon(_ribbon);
     _buttonSpecExpand   = new ButtonSpecExpandRibbon(_ribbon);
     _buttonSpecsFixed.AddRange(new ButtonSpec[] { _buttonSpecMinimize, _buttonSpecExpand, _buttonSpecMin, _buttonSpecRestore, _buttonSpecClose });
 }