Registers a particular plugin to the global system at the given name.
        
        :param      plugin  | <XWizardPlugin>

def register( cls, plugin ):
        """
        Registers a particular plugin to the global system at the given name.
        
        :param      plugin  | <XWizardPlugin>
        """
        if ( not plugin ):
            return
            
        if ( cls._plugins is None ):
            cls._plugins = {}
            
        cls._plugins[plugin.uniqueName()] = plugin