* GateIO: Fix GetFuturesContractDetails for Deliveries
Was returning the product of all the contracts, so 1444 instead of 38
contracts.
* GateIO: Fix GetOpenInterest returning asset.ErrNotEnabled
Using wrong error for pair not enabled
* GateIO: Rename GetSingleContract and GetSingleDeliveryContracts
Especially fixes GetSingleContract, which seems misleading to not say
Futures.
There's a load of `GetSingle*` here that should probably also be fixed,
but these two justified a dyno
* GateIO: Rename GateIOGetPersonalTradingHistory to GetMySpotTradingHistory
* GateIO: Rename GetMyPersonalTradingHistory to GetMyFuturesTradingHistory
* GateIO: Remove duplicate DeliveryTradingHistory
* GateIO: Rename Get*PersonalTradingHistory to GetMy*TradingHistory
* Linter: Disable shadow linting for err
It's been a year, and I'm still getting caught out by govet demanding I
don't shadow a var I was deliberately shadowing.
Made worse by an increase in clashes with stylecheck when they both want
opposite things on the same line.
* GateIO: Add missing Futures and tradinghistory fields
* GateIO: Improve WS Header parsing
This unifies handling for time_ms and time in response headers, since
options and delivery have only time, but spot has time_ms as well.
We use the better of the two results.
Also [improves performance 2x](https://gist.github.com/gbjk/7cacb63b9a256e745534bb05ca853c48)
* GateIO: Use time_ms WS fields where available
Removes the deprecated _time json fields and populates our Time fields
with the time_ms values