Add "Place Bulk Orders"

[unsphere]

Add support for "Place Bulk Orders"
https://docs.kucoin.com/#place-bulk-orders

Like that:

/* 
  Place Bulk Orders
  POST /api/v1/orders/multi
  Details for params see https://docs.kucoin.com/#place-bulk-orders
  General params
  params = {
    symbol: string,
    orderList: [
      {
          clientOid: string
          side: string ['buy' || 'sell]
          type: string [optional, default: limit] - limit or market
          remark: string [optional]
          stop: string [optional] - either loss or entry and needs stopPrice
          stopPrice: string [optional] - needed for stop 
          stp: string [optional] (self trade prevention)
          tradeType: string [optional, default: TRADE] - TRADE (Spot Trade), MARGIN_TRADE (Margin Trade)
          price: string,
          size: string,
          timeInForce: string [optional, default is GTC]
          cancelAfter: long (unix time) [optional]
          postOnly: boolean [optional] - Post only flag, invalid when timeInForce is IOC or FOK
          hidden: boolean [optional]
          Iceberg: boolean [optional]
          visibleSize: string [optional]
      }
    ]
  }
*/
api.placeBulkOrders(params)