Unregisters the given plugin from the system based on its name.
        
        :param      plugin | <Plugin>

def unregister(cls, plugin):
        """
        Unregisters the given plugin from the system based on its name.
        
        :param      plugin | <Plugin>
        """
        plugs = getattr(cls, '_%s__plugins' % cls.__name__, {})
        try:
            plugs.pop(plugin.name())
        except AttributeError:
            pass
        except ValueError:
            pass