Registers the given builder as a plugin to the system.
        
        :param      plugin | <subclass of PackageBuilder>
                    name   | <str> || None

def register(plugin, name=None):
        """
        Registers the given builder as a plugin to the system.
        
        :param      plugin | <subclass of PackageBuilder>
                    name   | <str> || None
        """
        if name is None:
            name = plugin.__name__

        Builder._plugins[nstr(name)] = plugin