store: [
        false,
        'the npm name or path of the storage module or callbacks file',
        'string',
        'greenlock-store-fs'
    ],
    'store-xxxx': [
        false,
        'an option for the chosen storage module, such as --store-apikey or --store-bucket',
        'bag'
    ],
    'store-json': [
        false,
        'a JSON string containing all option for the chosen store module (instead of --store-xxxx)',
        'json',
        '{}'
    ],