Add additional fields in orders response

It would be good if we add additional fields to the order response, like order validity, stop price, stop limit, post only. I know few exchange may lack few fields like post only which will be only available for maker taker exchanges. But fields like order validity and stops are common across all exchanges.

Here is an example from GDAX.

[
  {
    "id": "5ca4ccf3-4f14-48d4-bb4c-9799dbd06cd5",
    "info": {
      "id": "5ca4ccf3-4f14-48d4-bb4c-9799dbd06cd5",
      "price": "49.99000000",
      "size": "1.00000000",
      "product_id": "LTC-USD",
      "side": "sell",
      "stp": "dc",
      "type": "limit",
      "time_in_force": "GTC",
      "post_only": false,
      "created_at": "2017-10-23T23:54:20.499592Z",
      "fill_fees": "0.0000000000000000",
      "filled_size": "0.00000000",
      "executed_value": "0.0000000000000000",
      "status": "active",
      "settled": false,
      "stop": "loss",
      "stop_price": "50.00000000"
    },
    "timestamp": 1508802860499,
    "datetime": "2017-10-23T23:54:20.499Z",
    "status": "open",
    "symbol": "LTC/USD",
    "type": "limit",
    "side": "sell",
    "price": 49.99,
    "cost": 0,
    "amount": 1,
    "filled": 0,
    "remaining": 1
  }
]

[anandanand84]

@kroitor Validity is the time in force “time_in_force”: “GTC”, yes it is possible for an exchange to be invalid after a certain period of time, here is an example in gdax the valid values are good till cancelled, good till specified time( 1min, 1hour), immediate or cancel or fill or kill

[kroitor]

Reference: #233