exchanges/engine: Add multichain deposit/withdrawal support (#794)

* Add exchange multichain support

* Start tidying up

* Add multichain transfer support for Bitfinex and fix poloniex bug

* Add Coinbene multichain support

* Start adjusting the deposit address manager

* Fix deposit tests and further enhancements

* Cleanup

* Add bypass flag, expand tests plus error coverage for Huobi

Adjust helpers

* Address nitterinos

* BFX wd changes

* Address nitterinos

* Minor fixes rebasing on master

* Fix BFX acceptableMethods test

* Add some TO-DOs for 2 tests WRT races

* Fix acceptableMethods test round 2

* Address nitterinos

portfolio/portfolio_types.go

@@ -15,6 +15,7 @@ type Base struct {
 // Address sub type holding address information for portfolio
 type Address struct {
 	Address            string
+	AddressTag         string
 	CoinType           currency.Code
 	Balance            float64
 	Description        string

portfolio/withdraw/withdraw_types.go

@@ -60,6 +60,7 @@ var (
 type CryptoRequest struct {
 	Address    string
 	AddressTag string
+	Chain      string
 	FeeAmount  float64
 }