Load the .mlaunch_startup file that exists in each datadir.

        Handles different protocol versions.

def _load_parameters(self):
        """
        Load the .mlaunch_startup file that exists in each datadir.

        Handles different protocol versions.
        """
        datapath = self.dir

        startup_file = os.path.join(datapath, '.mlaunch_startup')
        if not os.path.exists(startup_file):
            return False

        in_dict = json.load(open(startup_file, 'rb'))

        # handle legacy version without versioned protocol
        if 'protocol_version' not in in_dict:
            in_dict['protocol_version'] = 1
            self.loaded_args = in_dict
            self.startup_info = {}
            # hostname was added recently
            self.loaded_args['hostname'] = socket.gethostname()

        elif in_dict['protocol_version'] == 2:
            self.startup_info = in_dict['startup_info']
            self.loaded_unknown_args = in_dict['unknown_args']
            self.loaded_args = in_dict['parsed_args']

        # changed 'authentication' to 'auth', if present (from old env) rename
        if 'authentication' in self.loaded_args:
            self.loaded_args['auth'] = self.loaded_args['authentication']
            del self.loaded_args['authentication']

        return True