`kucoin` backend: live order mgmt

[jaredgoldman]

Our Kucoin backend is ready to land for data-viz but still lacks a complete order-mode. Remaining tasks for full support include:

• [ ] Order mode functionality
  • [ ] buy
  • [ ] sell
  • [ ] short
  • [ ] cancel
• [ ] Complete user api
  • [ ] fetch balances
• [x] Update with work from #489

[goodboy]

@jaredgoldman i'm probably going to put up a small patch to get this up to snuff with #489 once i start landing commit factored history segments #272

I'll be sure to reach out.

[goodboy]

520 has much newer reference code, and probably a more similar approach for what will be needed here.

Of particular note is the .binance.api.Client's approach to multi-venue support for spot, USD-M and COIN-M futures market venues.