Rasa train API: Pass lookup tables

Hi, you can do it by adding the lookup table to nlu via json:

{
    "domain": "{your_domain}",
    "config": "{your_config}",
    "nlu": "## intent:example\n## lookup:CarManufacturer\n- BMW\n- VW\n- Dacia\n- Ford",
    "stories": "{your_stories}",
    "force": false,
    "save_to_default_model_directory": true
}